There is a saying: You can't scam an honest man.

If you are not being greedy and trying to take advantage of someone, you will not fall victim to these scams. Do not try to merch unless you have spent the time to understand the market. Learn what things cost, sell what you farm at appropriate prices, buy when you see something that is "on sale" and you will be ok. If it sounds too good to be true, it usually is.