Are flea markets good for old games at a good price?

That's like asking is a casino a good place to make money. Sure, I suppose there's that chance, but often it's just luck and most of what you see you can't be too sure about.

I, personally, have had bouts of great luck at flea markets and thrift stores... but it's a gamble. More than 75% of the time I find almost nothing, yet some days I hit the jackpot.