Hidden costs of custom trading platform development.
Costs that do not appear in engineering quotes for custom trading-platform projects.
The visible cost
Vendor quotes typically cover discovery, design, development, QA, deployment, and an initial support period. This figure understates total cost.
Data quality
A substantial fraction of engineering effort on any trading platform is data work that did not appear in the specification — reference data, corporate actions, broker-versus-vendor pricing discrepancies, administrator-versus-engine NAV differences.
Budget 20% above the engineering quote for data work that surfaces in production.
Operations
Vendor quotes generally cover construction, not operation. Live trading systems require monitoring during market hours, weekend maintenance, incident response, regulatory reporting, and quarterly compliance work.
Budget for operations from project inception. Retrofitted operations costs are materially higher.
Regulatory change
Financial regulation evolves. Each major update — MiFID II/R, FinSA, PRIIPs 2.0 — requires platform engineering.
Budget at least 10% of annual operating cost for regulatory engineering.
Integration upkeep
Platforms typically integrate with several external systems — market data, broker, KYC, payment, fund administrator. APIs change, formats change, providers are acquired.
Budget for integration maintenance, either internally or contractually.
Replacement
Custom trading platforms are commonly rewritten between the second and fourth year of operation, typically because the initial version was built under time pressure and accumulated debt.
Budget for replacement either by overinvesting in initial architecture or by planning the cost.
Total
A reasonable assumption is the visible quote plus 50%, with annual operating cost at approximately 30% of the build cost.