About a month ago, the PS3 version (not sure about X360) had a chain-wide "Instant Rebate" offering this for 29.99. I locked in a $25 gift card trade in at BestBuy, bought this game, played the heck out of it, then traded it in within the 30 day limit. I get tired of most games after just a couple weeks, so made sense to me. I did the same thing when Blur went on sale and had the $20 mfg coupon, just sent that in to the trade in service for a $32 dollar gift card, so they paid me $12 to "rent" Blur.
I plan to do this a lot more in the future, actually get paid to play games like they're longterm rentals. Lock in a game's TIV, buy it close to day one for as cheap as you can, then play it out within a month, trade it in and don't lose a lot of value, in some cases, make money. As long as I don't care about keeping the games, then makes sense to me.
Both S/S and Blur are great games too, recommend them for play.