The thing to remember about this genre of games is that most titles are pirated to hell and back, widely available for much less than you could possibly sell a hand-made reproduction for. Most Mega Drive games of this nature can be bought brand new for between $5-$10 USD, and that's with the reseller making a profit.
Quality labels and boxes cost an arm and a leg. You'd be lucky to find a print shop that will do nice vinyl lables for less than $2 USD each... and that's cutting them out to size by hand yourself. I wouldn't even want to know how much cardboard boxes are.
Although its entirely my opinion, most SNES pirates are really shitty games to be honest. Nobody is going to buy them to actually play, most would buy them as a collectible. Taking that into consideration, someone that really wants to buy the game can probably find it for a cheaper price than you can sell it for. To actually clear your overhead you'd basically need to sell to people that don't know a lot about unlicensed carts and can't get ahold of them themselves.
Don't take that as me shitting on your ideas; I have the utmost respect for repro makers that produce a quality product. I just wouldn't go into this particular area of games because it will be nothing but a money pit, you'd never get back your time and money invested in it. You'd probably be better to stick with the standard repro titles like translated RPG's, Japan-only action games, etc.
Just my .02