The verdict in three sentences
A fixed-price contract works when the scope is frozen and documented, but its price includes a 15 to 30% risk margin and every change goes through a change order. An agile retainer, billed 1,100 to 1,600 CHF per day in Zurich in 2026, follows the evolving need sprint after sprint, at the cost of more demanding steering on the client side. For a planning application whose business rules will move, the best compromise is often a capped time-and-materials budget with a fixed-price discovery phase.
How each model sets the price
On a fixed price, the vendor commits to an outcome and a price. It estimates the days, then adds a buffer for unknowns and ambiguous specifications. In a retainer, you pay the days actually used and the vendor commits to resources and a delivery rhythm (usually 2-week sprints).
| Criterion | Fixed price | Agile retainer |
|---|---|---|
| Price basis | Estimated days + 15 to 30% risk margin | Days used, 1,100 to 1,600 CHF per day |
| Vendor commitment | Outcome, deadline, price | Resources, transparency, velocity |
| Change in need | Priced change order, 1 to 3 weeks | Reprioritized at next sprint |
| Budget visibility | High at the start | Progressive, cap possible |
| Client workload | Writing the specification | Product owner 1 to 2 days per sprint |
| Main risk | Serial change orders, cut quality | Drift if backlog poorly prioritized |
| Discovery length | 3 to 6 weeks | 1 to 2 weeks then iterations |
These values are market estimates for Zurich in 2026.
The real cost: risk margin versus change orders
The fixed-price trap lies in change orders. On a business application, 20 to 40% of requirements commonly change during the project, because users discover their needs when they see the first screens.
| Scenario on a 120-day estimated project | Fixed price (1,350 CHF/day, 20% margin) | Retainer (1,350 CHF/day) |
|---|---|---|
| Base price | 194,400 CHF | 162,000 CHF if 120 days |
| Stable need (5% change) | 194,400 + 1 change order 8,100 = 202,500 CHF | 170,100 CHF (126 days) |
| Moderate change (20%) | 194,400 + change orders 38,880 = 233,280 CHF | 194,400 CHF (144 days) |
| Heavy change (40%) | 194,400 + change orders 77,760 = 272,160 CHF | 226,800 CHF (168 days) |
| Delay added by change orders | 3 to 8 weeks | 0 to 3 weeks |
Fixed-price change orders are often priced with the same risk margin, hence the gap. When the need is stable, fixed price remains a good visibility tool.
The hybrid model: fixed-price discovery, capped retainer delivery
The most robust setup in 2026 combines three layers. A fixed-price discovery (15,000 to 30,000 CHF) produces process maps, mockups and a prioritized backlog. Delivery on a retainer moves in 2-week sprints with a demo at the end of each. A contractual budget cap forces both sides to make trade-offs: once 80% of the budget is used, the version 1 scope is frozen.
| Clause to require | Fixed price | Retainer |
|---|---|---|
| Assignment of code rights | Yes | Yes |
| Git repository owned by the client | Yes | Yes |
| Change order priced within 5 days | Yes | Not applicable |
| Budget cap and 80% alert | Not applicable | Yes |
| Demo at each sprint | Recommended | Yes |
| Late delivery penalties | Yes, 0.5 to 1% per week | Rarely |
| Conformity warranty | 3 to 6 months | Per contract |
Mini case study
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Lukas, CFO of a 400-employee food processing group near Zurich, wants a production planning app for three plants. One vendor proposes a fixed price of 210,000 CHF for 130 estimated days at 1,350 CHF, risk margin included. Another proposes a 20,000 CHF fixed-price discovery, then a retainer at 1,400 CHF per day capped at 110 days, so 154,000 CHF. Lukas knows the scheduling rules of the Winterthur plant will be revised during the year: he expects 25% change. On the fixed price, with change orders at the same rate, the bill would reach about 262,000 CHF. In the hybrid model the capped total stays at 174,000 CHF, with the option to push secondary features to version 2. Gap: 88,000 CHF, in exchange for 1.5 days per sprint from his planning manager acting as product owner.
FAQ
Does a fixed price really protect against overruns?
It protects against overrunning the estimated days, not against a changing need. With 20% of requirements modified, the final bill often exceeds the initial price by 15 to 25%.
What day rate should I expect in Zurich in 2026?
Market estimates range from 1,100 to 1,600 CHF per day depending on seniority and firm size, among the highest rates in Europe.
Can a retainer be capped?
Yes, with a maximum budget and a contractual alert at 80% consumption. On a 150,000 CHF cap, the alert triggers at 120,000 CHF and forces a scope decision.
How much time must the client give an agile retainer?
Plan 1 to 2 days per 2-week sprint for the product owner, or 10 to 20% of their time. Without that availability, the retainer drifts.
What budgets apply for custom business software with Kolonell?
A simple application is priced from 2,500,000 to 4,000,000 FCFA (3,810 to 6,100 EUR), a medium one from 4 to 7 M FCFA (6,100 to 10,670 EUR) and a complex one from 7 M FCFA (10,670 EUR), fixed price or in phases.
Let's scope your project. Describe your processes and how stable your business rules are: we will recommend the right contract model and price discovery, delivery and the budget cap. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
