The current top-up rates make Lite + 150-minute add-on a strictly better deal than Pro for any AI-led customer. This document quantifies the cannibalization, lays out provider unit costs in full, and proposes a restructure that fixes the ladder while preserving healthy margin.
Sourced directly from each provider's pricing page in May 2026. All figures converted to GBP at 0.74. Update FX or any unit cost in the spreadsheet companion to recalculate the entire model.
| Item | USD | Unit | GBP | Notes |
|---|---|---|---|---|
| Twilio (UK) | ||||
| UK local number | $3.50 | per month | £2.59 | Voice page rate; SMS page lists $1.15. Use higher figure for safety. |
| UK mobile number | $3.50 | per month | £2.59 | Same rate as local on voice page. |
| Inbound voice (local) | $0.0100 | per minute | £0.0074 | Cost to receive a call. |
| Outbound voice (UK local) | $0.0158 | per minute | £0.0117 | Calls to UK landlines. |
| Outbound voice (UK mobile) | $0.0305 | per minute | £0.0226 | Calls to UK mobiles. |
| Media Streams (audio relay) | $0.0040 | per minute | £0.0030 | For sending audio to Deepgram / ElevenLabs. |
| SMS outbound (mobile) | $0.0560 | per segment | £0.0414 | Per 160-character segment. |
| SMS inbound | $0.0075 | per segment | £0.0056 | Inbound SMS fee. |
| Deepgram | ||||
| STT only (Nova-3, PAYG) | $0.0077 | per minute | £0.0057 | Plain speech-to-text. £0.46/hr. |
| Voice Agent BYO LLM+TTS | $0.0500 | per minute | £0.0370 | If using Deepgram orchestration with your LLM/TTS. |
| Voice Agent Standard (bundled) | $0.0800 | per minute | £0.0592 | Full STT+LLM+TTS bundled. |
| Anthropic (Claude Sonnet 4.6) | ||||
| Input tokens | $3.00 | per 1M tokens | £2.22 | Caching cuts to $0.30/M. |
| Output tokens | $15.00 | per 1M tokens | £11.10 | Sonnet 4.6 list price. |
| Assumed tokens / minute | 1,500 in | + 300 out | £0.0067 | Effective per-minute Claude cost at typical conversation length. |
| ElevenLabs | ||||
| Flash / Turbo TTS (Business tier) | $0.06 | per 1k chars | £0.0444 | Lowest API rate; assumes Business plan ($1,320/mo). |
| Multilingual v2 / v3 TTS | $0.12 | per 1k chars | £0.0888 | Higher quality, double the cost. |
| Assumed chars / minute | 750 | chars | £0.0333 | ~150 spoken words/min using Flash. |
| SendGrid | ||||
| Essentials plan fixed cost | $19.95 | per month | £14.76 | Up to 50,000 emails/month. |
| Effective cost / email at 25k/mo | $0.0008 | per email | £0.0006 | Marginal cost essentially zero at scale. |
| → True cost per AI voice minute (full stack) | £0.0560 | Twilio inbound + Media Streams + Deepgram STT + Claude Sonnet 4.6 + ElevenLabs Flash | ||
Of the £0.056 cost per AI minute, roughly 59% is ElevenLabs (£0.033), 17% is Twilio (£0.010), 12% is Claude (£0.007), 10% is Deepgram (£0.006), with SendGrid trivial. Biggest savings levers: prompt caching on Claude (cuts £0.0067 → ~£0.0015) and ensuring you're on ElevenLabs Business tier for the £0.06/1k char rate.
Cost & profit assuming the customer uses 100% of their allocated minutes, numbers, and credits — the worst case for margin. Most customers won't use everything, so real margins run higher.
| Plan | Price | Numbers | Inc. min | AI min | Emails | SMS | Cost | Profit | Margin | £/AI min |
|---|---|---|---|---|---|---|---|---|---|---|
| Starter | £9.99 | 1 | 50 | 0 | 0 | 0 | £2.96 | £7.03 | 70.4% | — |
| Lite | £19.99 | 2 | 250 | 20 | 50 | 20 | £9.01 | £10.98 | 54.9% | £1.00 |
| Pro | £79.99 | 3 | 750 | 100 | 100 | 100 | £23.13 | £56.87 | 71.1% | £0.80 |
| Enterprise | £199.99 | 10 | 1,500 | 300 | 200 | 200 | £62.21 | £137.78 | 68.9% | £0.67 |
The £/AI min column tells the story: a Pro customer is effectively paying £0.80 per AI minute embedded in their plan, while the same customer can buy AI minutes on top-up for £0.166 each. That's a 5× spread — the foundation of the cannibalization.
Margin per pack. Healthy on absolute terms — the issue isn't that top-ups lose money, it's that they're priced so far below the in-plan AI minute rate that they undercut the ladder.
| Pack | Price | Quantity | Charged £/unit | Cost £/unit | Total Cost | Profit | Margin |
|---|---|---|---|---|---|---|---|
| AI Voice Minutes | |||||||
| 150 AI mins | £24.99 | 150 | £0.1666 | £0.0560 | £8.40 | £16.59 | 66.4% |
| 500 AI mins | £79.99 | 500 | £0.1600 | £0.0560 | £28.01 | £51.98 | 65.0% |
| 1,000 AI mins | £149.99 | 1,000 | £0.1500 | £0.0560 | £56.02 | £93.97 | 62.6% |
| 2,000 AI mins | £319.99 | 2,000 | £0.1600 | £0.0560 | £112.04 | £207.95 | 65.0% |
| 2,500 AI mins | £399.99 | 2,500 | £0.1600 | £0.0560 | £140.05 | £259.94 | 65.0% |
| Incoming / Outgoing Minutes | |||||||
| 250 mins | £10.99 | 250 | £0.0440 | £0.0074 | £1.85 | £9.14 | 83.2% |
| 500 mins | £21.99 | 500 | £0.0440 | £0.0074 | £3.70 | £18.29 | 83.2% |
| 1,000 mins | £42.99 | 1,000 | £0.0430 | £0.0074 | £7.40 | £35.59 | 82.8% |
| 2,000 mins | £85.99 | 2,000 | £0.0430 | £0.0074 | £14.80 | £71.19 | 82.8% |
| Phone Numbers | |||||||
| 1 number | £5.99 | 1 | £5.99 | £2.59 | £2.59 | £3.40 | 56.8% |
| 5 numbers | £24.99 | 5 | £5.00 | £2.59 | £12.95 | £12.04 | 48.2% |
| 15 numbers | £64.99 | 15 | £4.33 | £2.59 | £38.85 | £26.14 | 40.2% |
| 50 numbers | £169.99 | 50 | £3.40 | £2.59 | £129.50 | £40.49 | 23.8% |
| SMS Packages | |||||||
| 500 SMS | £39.99 | 500 | £0.0800 | £0.0414 | £20.72 | £19.27 | 48.2% |
| 1,500 SMS | £109.99 | 1,500 | £0.0733 | £0.0414 | £62.16 | £47.83 | 43.5% |
| 3,000 SMS | £199.99 | 3,000 | £0.0667 | £0.0414 | £124.32 | £75.67 | 37.8% |
| 10,000 SMS | £599.00 | 10,000 | £0.0599 | £0.0414 | £414.40 | £184.60 | 30.8% |
| Email Packages | |||||||
| 1,000 emails | £14.99 | 1,000 | £0.0150 | £0.0006 | £0.59 | £14.40 | 96.0% |
| 5,000 emails | £59.99 | 5,000 | £0.0120 | £0.0006 | £2.96 | £57.03 | 95.1% |
| 15,000 emails | £139.99 | 15,000 | £0.0093 | £0.0006 | £8.88 | £131.11 | 93.7% |
| 50,000 emails | £289.99 | 50,000 | £0.0058 | £0.0006 | £29.60 | £260.39 | 89.8% |
The 50-number pack at 23.8% margin is dangerously thin — if Twilio raises UK number fees even slightly, that line goes negative. The 10,000 SMS pack at 30.8% margin is also low for the volume. Email packages are extremely profitable (90%+) because SendGrid's marginal cost is essentially nil — could afford to discount these aggressively as upsell hooks.
The change is concentrated entirely on AI minute allocations. Lite gets 10 more, Pro gets 150 more, Enterprise gets 450 more. Prices stay flat across all tiers — the margin hit is absorbed deliberately to make the upgrade story cleaner for customers.
| Plan | Price | Numbers | Inc. min | AI min | Emails | SMS | Cost | Profit | Margin | £/AI min |
|---|---|---|---|---|---|---|---|---|---|---|
| Starter | £9.99 | 1 | 50 | 0 | 0 | 0 | £2.96 | £7.03 | 70.4% | — |
| Lite | £19.99 | 2 | 250 | 30 | 50 | 20 | £9.57 | £10.42 | 52.1% | £0.67 |
| Pro | £79.99 | 3 | 750 | 250 | 100 | 100 | £31.53 | £48.46 | 60.6% | £0.32 |
| Enterprise | £199.99 | 10 | 1,500 | 750 | 200 | 200 | £87.42 | £112.57 | 56.3% | £0.27 |
Holding prices flat means absorbing a bigger margin hit: Pro drops 10.5 percentage points (71% → 60.6%) and Enterprise drops 12.6 points (69% → 56.3%) at full utilisation. Both still comfortably above the 50% SaaS gross-margin floor. In practice most customers don't max out their allocations, so realised margins run higher. The trade buys you a coherent ladder where every tier visibly outperforms the one below — and a more attractive upgrade path because the price gap to Pro is £25 rather than £35.
AI minute packs repriced upward and the volume curve steepened. Smallest pack now starts at £0.233/min, largest drops to £0.140/min — committed buyers see real volume reward. Other categories left unchanged for now (different problem, separate decision).
| Pack | Old price | New price | Δ | New £/unit | Cost | Profit | Margin |
|---|---|---|---|---|---|---|---|
| AI Voice Minutes (the change) | |||||||
| 150 AI mins | £24.99 | £34.99 | +£10.00 | £0.2333 | £8.40 | £26.59 | 76.0% |
| 500 AI mins | £79.99 | £99.99 | +£20.00 | £0.2000 | £28.01 | £71.98 | 72.0% |
| 1,000 AI mins | £149.99 | £169.99 | +£20.00 | £0.1700 | £56.02 | £113.97 | 67.0% |
| 2,000 AI mins | £319.99 | £299.99 | −£20.00 | £0.1500 | £112.04 | £187.95 | 62.7% |
| 2,500 AI mins | £399.99 | £349.99 | −£50.00 | £0.1400 | £140.05 | £209.94 | 60.0% |
| Other categories — unchanged | |||||||
| Incoming/outgoing minutes, phone numbers, SMS packs, and email packs all stay at current prices for this round. The 50-number pack and 10,000 SMS pack are flagged as future review items. | |||||||
Note the volume curve flips direction: the smallest pack is now the most expensive per minute (76% margin) while the biggest pack is the cheapest per minute (60% margin). This is deliberate — small top-ups absorb light-usage spillover at premium pricing, while bulk packs reward serious commitment.
Same customer, same need: 150–250 AI minutes per month. Today they should rationally pick Lite + top-up because Pro is dominated. After the fix, Pro becomes the right answer for anyone needing more than 180 AI minutes.
Bump Pro from 100 AI min to 250 AI min while holding the price at £79.99. That single change kills the most egregious cannibalization (the £35-cheaper-AND-more-minutes path) and turns Pro into a £25-more-for-70-extra-AI-min decision instead. Everything else in this doc is optimisation on top of that core fix.