I do my best to avoid fake games, as I 100% don't want to own any. I've never had to open a game in a shop before, but I do own a lil' 'travel set' of gaming screwdrivers & cleaning stuff in case I do ever need/want to do some serious field testing.
What bothers me about repros, aside from often using cheap parts that will either break down quickly or not be compatible with every system revision, is the 'con'. These are not liscensed copies, these are generally some factory in China that stole a ROM, flashed it, and sold it for a crazy markup. Oddly enough, it's usually the markup that gets me... if we both know you stole it, and it only cost you a couple bucks to make the cart, why am I supposed to pay $20 for it? Or worse- they charge full market value to try and hide the fact that it's a repro and make more money. Some makers of repros have the best of intentions, but it still just ends up facilitating some very scummy behavior.
As the consumer- if you don't care about owning the original, just get yourself a RetroPi or an Everdrive and download your own ROMs. It'll be cheaper in the long run than paying someone to steal for you.