I created an online market for a game that sold in-game items with revenue at its peak of over $300k USD per month. Initially it just used eBay affiliate links, but since I would track the sellers in my database, I reached out to the big wholesalers and encouraged them to go nearly exclusive on my market for a similar cut. It was all built over a few years and it runs mostly on autopilot, all marketing, hosting, and code built by me. Never discussed it on any forum before.