What would this actually cost to build?

It is a planning estimate, not a quote. The numbers come from typical hour ranges for each feature, multiplied by a blended freelance-to-agency rate of $85 to $145 an hour. Real quotes vary widely depending on how clearly the work is described, who you hire, and where they are based. Use it to sanity-check a quote you have been given, not to replace one.

Most small first versions land between $5,000 and $40,000 when you hire someone. The biggest drivers are user accounts, payments, an admin area, and messaging between users. Building the same first version yourself with AI tools typically costs $20 to $60 a month in subscriptions plus your own time.

In money, almost always. In time, you are taking on the hours yourself. That trade works well for a first version you want to test, and works badly once payments, live data, or other people's private information are involved, where a mistake costs more than the build.

No. The calculator runs entirely in your browser. Nothing is sent anywhere, there is no sign-up, and there is no account to create.