I think digital should be 10-15 less than physical. I only say this because there is no way of trading or selling them once in your account, unlike physical games. If they could figure this little thing out, Then I have no problem paying more.
It's pretty apparent that both Sony, and Microsoft want a digital future, but they also dont want to piss off their brick and mortar retailers where most casual gamers go to buy games. The solution for that is simple. Replace all the physical games with download cards instead. (like the PS+, Xbox Live cards) thereby giving retailers the ability to still sell games, (while also holding more stock, and using less physical space.)







