I have seen unopened on-card N comabt grips sell for $175-$300 on the websites. Once you open them they are just another old pair of stocks, worth $100-200 at auction depending on the bidders.
Damage from plastic? As someone who collects grips on the card, I have many that are older than I am (40+ years) and the grips have no damage at all inside, clear as day to see.
If you have not opened them yet, please wait. You will be destroying a real collector's item and turning them into another set of combats. Maybe I shouldn't talk, as I've bought NIB guns and fired them when people might wince - but I have a special affinity for grips.
From the pool of available N-frame original combat stocks available, only some of them are in great shape. Of those, only some are in excellent-to-mint shape. Of those, fewer still have been never put on a gun. And of those, the smallest percentage is obviously those that have never been opened from their original manufacturer's packaging. Don't downgrade them one category unless you can't find mint stocks anywhere else - and at the price you paid, you both got a good price on the closed package and paid the high end of already-opened mint stocks. Keep them closed!
