As for OP, I don't know of a resale value being specified for 3E, but often DMs used what got put into 4E anyway as that is sensible, why do you think it got put into 4E? Some adventures would specify resale price, such as Age of Worms which states the merchants pay 95% for gems, 30% for equipment.
Now admittedly the sale price makes somewhat less sense in 4E than it did in 3E since identify doesn't cost 100GP for a merchant, just 5 minutes time, and there aren't spells to put fake auras on items so there is less risk to the merchant, and items can be resized, so that female orc breastplate which a merchant would NEVER EVER EVER be able to resell for anything but scrap could actually be used for something.
The issue to me isn't selling to merchants; both 4e and 3e make it clear that if you sell to a merchant or do your selling "off screen", you'll be shafted, and this is both acceptable and "realistic" -- ask anyone who'se sold Magic cards to a vendor.

The problem is that 3e leaves open the possibility of PCs finding non-merchants to sell to, while 4e (at least for rituals) comes right out and states "No one will pay more than half price; anyone who might be tempted to already has their own ritual books and dedicated scroll makers. Sucks to be you." The reasoning, from a game balance perspectice, is obvious -- there's no limits on scroll manufacture. If you have clients, turning mastered rituals into scrolls is easy money, and since 4e dropped the wealth limits by town, there's no end to what you could make. So, instead of more elegant solutions, 4e just slams down an absolute. (Of course, the DM can ignore it. The DM can ignore any rule he doesn't like, in any system, in any game. It's a meaningless answer, as it effectively says all criticism, whether of a crude means of solving a game balance problem or of a broken power/spell/monster, is null.)
As I said above, though, I don't want to get bogged down in economics. Nitpicking particular details isn't my concern here. Others have said "4e lets you be a HERO!" Well, fine. A hero defending WHAT? A world which pretty much only exists to let him look heroic defending it?
My ability to care about defeating the Big Bad in a game is directly proportional to my ability to care about the world I'm allegedly saving, to immerse myself in this alternate reality. Maybe I'm wrong, and in the hands of a skilled DM, I will find 4e to be just as immersive as 3e was. It just seems to me that in 4e, the DM has to do a lot more work to make the world "come alive", to hide the edges of the sets and keep the mikes out of the shot, because the game rules are more intrusive than ever.