Real- time price calculations are gonna be hard to implement because of the constantly changing data, and finding a reliable source for current price info that reflects actual cost value. For example, akai katana(x360) says its $5.51 in estimate value, but I'm assuming that's disk only since complete copies are around the $11-14 w/o shipping for the regular edition. Amazon is ok for some price data, but on other items the price data is totally off when coming to used or new copies. So in order to program real time price calculation will be a huge undertaking to implement the site and something that's probably not gonna happen anytime soon, so just put your price you paid for games to calculate your collection prices, and compare to the going rate from multiple sites to make sure the actual value of your items are correct.