I spent a little time at the mall today. I saw 4 used copies of Ground Zeroes for both 360 and PS3. Almost got a ps3 version, but couldn't bring myself to even after birthday coupon.
I don't know how big you are on replaying/collecting/achievements/trophies, but I've beat the main mission once and all the side ops outside of the one you have to unlock and I'm a bit over 6 hours in, gonna get the rest of the collectibles and try for some of the S rankings as well. I don't think I'm going to replay it again on Hard mode although that and these trials that you unlock are also more things to go for. I would have been sad for $40/32 (what the next-gen was originally), but I was okay with paying $24 for it.