When GAME boost the price to £30 at the same time as offering them in a "2 for 1", thus forcing unsuspecting parents to buy 2 at a time at the price they should retail for in the first place then yeah, sadly I suspect they make quite a bit from them.
I can't completely bitch at GAME, while their new sale is rather lousy their sale on preowned DS titles is actually not bad; picked up POR for £13 last week
Hmm...you seem convinced it's fact. Well, it's not. The "Seal of Quality" really was to assure people that the carts were genuine and would work with your Nintendo device (unlike unlicensed games [which didn't carry the seal]). This was because back in the NES/SNES days, Nintendo had supreme control over cart production in the US (at least). They limited how many games a company could produce and were in charge of cart manufacturing.
...which is why Castlevania III got a crappy sound chip compared to its Japanese counterpart.