Sports and Rookie Cards Mint But Not Centered -- Anyone Know value?

I just looked up Ken Griffey Jr. 1989 Rookie Upper Deck on ebay and it's overvalued by a lot of sellers, just look at sold listings and you'll see what I mean. Gem mint 10 are rare so can command higher prices. Vast majority of cards are not GM-10. Grading plays a huge part in value of cards and such.

Off centering can knock off some grading points for certain.

Not a lot of cards of that era (80's, 90's) are worth grading. Not saying there is no market for it, but don't get your hopes up on thinking you're siting on a small fortune of baseball cards.

I suggest looking up all the cards you have that you think have some worth and checking the ebay sold listings and current listings to get an idea of what you have.

Type in PSA to show graded cards, as that is a big selling point.

Thanks. I got a Don Mattingly o-pee-chee rookie that's supposed to be 10x rarer than the topps one. Not looking to make a killing but I see them listed for like $350-400 for the topps one (will check the sold listings later, thanks for the tip). most of the other ones are listed at between say $3-50. Think I can get the grading for about $15 per card. Got about 10-15 that might get $50-plus. So, you'd say i should consider grading those handful? don't mind spending $200 on grading to check it out.