The pitch sounds identical
Every major platform now offers some version of the same story: AI agents that automate your workflows, answer your team's questions, and connect your business data. The language is interchangeable. The results are not.
The gap between the marketing and the reality matters most for small and mid-sized businesses, because SMBs cannot absorb a bad technology bet the way a 10,000 person enterprise can. A wrong call here means six months of sunk costs and a painful migration.
What each platform actually costs
Published pricing for AI agent capabilities across the four major platforms, converted to GBP at current rates. These are entry-level figures for a team of 20.
| Platform | AI agent cost | Base platform required | 20-person monthly total | Lock-in |
|---|---|---|---|---|
| Microsoft Copilot | ~£15/user/month | M365 Business (~£10/user/month) | ~£500/month | Annual commitment |
| Salesforce Agentforce | ~£20/user/month + £1.60/conversation | Starter Suite (~£20/user/month) | ~£800+/month | Annual contract |
| Google Gemini | Bundled with Business Standard | Business Standard (~£11/user/month) | ~£220/month | Annual for lower rate |
| HubSpot Breeze | ~£0.40/resolved conversation | Pro Hub (~£72/month base) | ~£150+/month | Annual typical |
| Custom AIOS | One-time build from £4,500 | None | Under £5 infrastructure | You own the code |
The numbers tell the first half of the story. A 20 person team on Microsoft Copilot pays £6,000 a year for AI agent access alone, on top of their existing M365 licences. Salesforce pushes past £9,600. These are recurring costs with no exit ramp.
The compounding problem: most SMBs do not use just one platform. They run a mix of Microsoft, Google, Xero, Slack, Simpro, and half a dozen vertical tools. Each platform's agents only see their own data. So you end up paying multiple per-seat fees for AI that cannot talk across your actual business.
Five problems every platform shares
1. Per-seat pricing punishes growth
Every platform charges per user, per month. Hire five more people and your AI bill jumps by £75 to £100 a month, permanently. A custom system charges nothing per seat because the infrastructure cost is fixed at pennies.
2. Agents only see one silo
Microsoft's agents read Microsoft data. Salesforce's agents read Salesforce data. Google's agents read Google data. None of them can natively reach into Xero, Simpro, your job management system, or the spreadsheet your operations manager actually runs the business from. Connecting external data requires custom integrations that typically add 20% to 40% to the published licence fee.
3. You own nothing
The agent logic, the prompts, the workflow configuration, the trained context: all of it belongs to the platform. Cancel your subscription and it disappears. With a custom AIOS, you own every line of code. You can modify it, move it, or hand it to any developer. It is yours.
4. Vendor lock-in is structural, not just contractual
After 12 months of building workflows, training agents on your data, and integrating your team's processes into the platform, switching costs are enormous. This is by design. The longer you stay, the harder it becomes to leave. Platform incentives and your business interests diverge over time.
5. Hidden costs surface late
Consumption billing (Salesforce's per-conversation charges, HubSpot's outcome pricing) sounds affordable at low volumes but becomes unpredictable as usage grows. Practitioners report 70x to 120x cost spikes when agents run multi-step workflows compared to simple queries. You will not see this in the sales deck.
What a custom AIOS looks like in practice
A custom AI Operating System is a single, purpose-built platform that replaces the patchwork. It connects the data sources your business actually uses, automates the workflows your team actually runs, and gives you an AI layer that sees across every part of the operation.
- No per-seat fees. The system costs pennies a month to run, regardless of how many people use it.
- Your data stays yours. Everything runs on infrastructure you control. No third party processes your business data unless you choose it.
- Built for your business, not every business. Enterprise platforms are built for the average of 100,000 companies. A custom AIOS is built for one: yours.
- Full code ownership. The source code is delivered to you. No dependency on any single provider continuing to exist.
- Flat cost structure. A one-time build fee, then infrastructure at under £5 a month. No consumption surprises.
When enterprise platforms make sense
To be fair: if your business already runs entirely inside one ecosystem (all Microsoft, or all Salesforce) and you have 200+ employees, the platform agent may be the right call. The integration is native, the per-seat cost amortises across a large workforce, and you probably have an IT team to manage it.
But most SMBs are not in that position. Most SMBs use three to five different tools, have under 50 people, and cannot justify £500+ a month for AI that only sees a fraction of their data.
The real question
The decision is not "which platform's AI agent should we subscribe to." The decision is whether you want to rent intelligence from a vendor who controls the terms, or build an operating system you own outright.
One path costs more every year. The other costs once.