When it comes to sportscards pick a few brands and stick with them if not, the card business will drive you crazy and suck every dollar out of you. Google wholesale sportscards. Many wholesalers will sell there products at cost just to stay in good standing with the maufactures. If a product offer comes out that is hot, of course the price will be more.
You can make more money by braking up boxes for singles. Rookies, game used, autographed and very low print cards is what to look for. Do your homework, there is money to be made.