The expensive parts are not the ones you expect
When people describe a marketplace, they think of listings and search. In practice those two blocks are under a third of the budget. The rest goes into access rights, recurring billing and moderation — everything that does not show up on a mockup.
The six blocks of a marketplace
1. Accounts and verification (15%). Two distinct populations, with different sign-up journeys. If accounts must be approved by hand, you also need the tool to do it.
2. Catalogue and search (20%). Publishing, filters, sorting. The hard part is not search: it is deciding which fields are public and which stay hidden.
3. Access rights (20%). The most underestimated line. Who sees which listing, at what level of detail, and under what condition. This is the logic that makes a confidential platform valuable, and it is tested line by line.
4. Subscriptions (15%). Plans, trials, mid-period changes, failed charges, cancellations. Far heavier than a one-off payment.
5. Messaging (10%). So conversations stay on the platform — otherwise both sides swap addresses in the first message and your business model disappears.
6. The back office (20%). Account and listing approval, dispute handling, access logs. Without it, you administer your platform from the database.
What always gets forgotten
Empty states. A marketplace that is empty at launch still has to look presentable and credible. Plan too for how you will seed both sides of the market: that is a commercial problem, but it has technical consequences.
Realistic ranges
- €35,000–60,000: one population per side, simple subscription, manual moderation
- €60,000–120,000: fine-grained access rights, several plans, external integrations
- beyond that: user-to-user payments, escrow, sector compliance
These are ranges for a first usable version, not a prototype. A prototype costs less and teaches you little: platforms are judged on real usage.