All traders want to always buy Bitcoin at a price cheaper than the market price. Apart from buying and selling on the ordinary, centralized crypto asset exchange, there is another option, namely a peer-to-peer exchange. In this exchange, asset prices are not “regulated” by the exchange manager, but directly by the users.
That's not exactly cheap, on P2P exchanges you can buy Bitcoin maybe 2-3% less than the market price if you're lucky which is not that much specially in crypto market, you can just as easily make that much by just swing trading bitcoin for a few hours or less.
The only upside to P2P exchanges is for people that are looking for a more decentralized way to exchange their Fiat or whatever to BTC, and it's specially true for those who are trying to exchange bigger amounts that would require going through KYC on centralized exchanges.