Well not if you're a consumer. If you're a consumer and you go into Tescos, who at the time were selling 3DS's for £175 quid, and they've got none left because the Game next door has bought them all up and is selling them for £220 (as Game were), how is that good for you? Game shops weren't allowed to sell any of their 'mint condition second hand' 3DSs until all their own allocation of 3DS's were sold at 45 quid higher price. If I was in the market for buying a 3DS, I'd look at it as Game attempting to use it's business funds to stop the consumer getting the best price possible and to make a bit of extra profit directly at the consumer's expense. It may be legal, but I find it utterly disreputable. Not that I previously considered Game to have much of a reputation anyway, but there you go.
Jon