My own one experience with taking someone to small claims court (a car repair shop) ended up with them paying what I asked for right after they got their summons. It is a fairly simple way to put pressure on someone.
Another -- if a person wanted to play hardball -- would be to find out if the seller is complying with all the state regulations regarding small businesses, such as having a sellers permit and collecting sales tax and reporting income. Many are not (if they're using CashApp, they quite possibly are trying to fly under the radar) and are thus in a very weak position if a scammed purchaser wanted to push things legally.