Ben's Bowman card is listed at $6-$15, and is only that high because he has done so well. You'd be better off to wait until the novelty wears off in the off-season. If you want to collect some of his rookie cards, try and get a limited release card like his Upper Deck Star Rookie. It lists at $20-$35, and you can probably get one for around $25 on eBay. I bought 2 recently, and think they'll hold value provided he lives up to all the hype.
If you want to check the prices of cards, go to: Beckett.com
and you can check the price of a single card to "try" their service, or for like $4 you can use the service for a month. Good luck if your buddy will part with the card for a few dollars.