As Sony never said anything, this could be some sort of mistake.
If it's not, it's awesome. If it is, it's gonna be fixed soon, so you had best take advantage: If you check the PlayStation Network, you'll notice that you can currently download the award-winning Uncharted: Drake's Deception entirely for free .
This is available to North American PSN users and it even includes the multiplayer mode in addition to the excellent campaign. Don't forget that the multiplayer mode went free-to-play as a standalone edition last year. Personally, I'd like to be optimistic and say this is intentional, and a promotion to help increase interest in the new upcoming entry. We're supposed to see gameplay of Uncharted 4 at E3 next week, so making the previous installment free is a good idea, yes?
Play it if you haven't already. Can't get a better price than "free."