Day 146: Every Pricing Model Has an Expensive Month
The following suppliers, tariffs and workloads are completely fictional. They are a pricing-risk illustration, not a market benchmark, client result, named-vendor comparison or ZSA price promise.
In this example, £0.012 per action looks smaller than £80 per user. But the useful procurement question is not which number looks cheaper. It is which pricing model creates the expensive month your budget can tolerate.
AI-assisted research may place unlike published price units beside each other during supplier discovery. No answer-engine output was tested for this post. The worksheet begins after discovery: it converts two fictional tariffs into budget exposure for one team.
Fix the team, then stress the tariff
The fictional buyer has 20 named users. The two fictional suppliers have equivalent fit, scope and implementation feasibility for the requirement.
Hypothetical tariff table — every figure and rule below is invented for this worked example.
| Supplier | Fictional charging rule | Exposure created |
|---|---|---|
| Supplier A: Seat | £80 per named user each month. All 20 users receive equal access, and there is no action surcharge across either modelled workload. | The buyer funds available access even when activity is light. |
| Supplier B: Usage | No seat fee for the same 20-user access. A £400 monthly minimum includes 40,000 completed actions; each additional action costs £0.012. | The buyer carries action-volume cost above the allowance. |
Only completed-action volume changes between the two months:
- Normal month: 20,000 completed actions.
- Stress month: 200,000 completed actions.
This holds team size, access, fit and scope constant. The comparison therefore isolates the budget exposure created by the charging rules rather than changing the organisation to manufacture a different winner.
The two-month worksheet
| Fictional monthly bill | Normal month: 20 users, 20,000 actions | Stress month: 20 users, 200,000 actions |
|---|---|---|
| Supplier A: Seat | 20 × £80 = £1,600 | 20 × £80 = £1,600 |
| Supplier B: Usage | £400 minimum + £0 overage = £400 | £400 + (160,000 × £0.012) = £2,320 |
The normal month rewards the usage tariff. Supplier B costs £400 rather than £1,600, a £1,200 saving.
The stress month rewards the seat tariff. Supplier A costs £1,600 rather than £2,320, a £720 saving.
Neither supplier changed. The 20-person team did not change. Under these fictional rules, one tariff monetises access and the other monetises activity. That difference determines where the budget absorbs uncertainty.
Supplier A asks the buyer to accept unused-capacity exposure: the £1,600 bill remains even when activity is low. Supplier B asks the buyer to accept volume-spike exposure: the minimum is lower, but cost rises once activity crosses the included allowance.
Neither pattern is universally cheaper. Each protects the budget from a different month.
Mark the crossover, not a universal winner
For this fixed 20-user team, Supplier A costs £1,600 every modelled month. Supplier B reaches the same bill at 140,000 completed actions:
40,000 included actions + ((£1,600 − £400) ÷ £0.012) = 140,000 actions
At exactly 140,000 actions, the fictional bills are equal. Below that boundary, Supplier B has the lower modelled bill. Above it, Supplier A has the lower modelled bill.
The crossover is a decision boundary, not a forecast. It does not show how often the team will enter either range, and it does not establish annual cost. A real purchase would still require current contract terms, definitions, caps, support costs, implementation costs and credible workload data. The worksheet proves only the arithmetic of the invented rules.
That boundary is still commercially useful. It turns a vague preference for “predictable pricing” into a visible trade-off:
- Choose Supplier B to capture the £1,200 normal-month saving, while accepting action-volume exposure above the allowance.
- Choose Supplier A to cap the modelled stress month at £1,600, while accepting the cost of named access during quieter periods.
Put the exposure in the approval record
A procurement note for unlike pricing units can be short:
- Normal-month bill: Supplier A £1,600; Supplier B £400.
- Credible stress-month bill: Supplier A £1,600; Supplier B £2,320.
- Exposure accepted: unused named-access capacity or action volume above 40,000.
The commercial choice is not “which fictional supplier is cheaper?” Both take that position under different workloads.
The choice is whether the organisation values the normal-month saving enough to carry the stress-month spike, or values stress-month protection enough to fund capacity when activity is light.
Every pricing model gives the buyer a different expensive month. Compare that month before approving the supplier.