I collect retro video games and often pick up cartridges that have price stickers and marker on them. I think a lot of collectors avoid them because they don’t look appealing, but it’s actually pretty easy to clean up a cartridge as long as there isn’t too much gunk on the actual label. Sharpie can come off by covering it with a dry erase marker, or by even applying a bit of hair spray to a paper towel and then gently wiping. Stickers can be quite tough to get off, but I can usually get one off by using a Clorox wipe. They have just enough grit to remove the sticker without scratching the cart.
Here’s some before and after shots with a copy of Super Mario 64: