the Mario Kart 8 sales numbers are going to be insane for June, I know a ton of people who bought 3, 4, 8, etc copies as for a week you could actually MAKE money buying MK8. Buy at Target for $35 per copy (after amazon PM and $15 discount coupon), trade into Best Buy/Gamestop for $44, keep CN code worth $15-20 (or a free game). I bought 4 copies myself. A slightly worse deal still going on Target this week (buy 3 copies for $98, trade in all 3 for $95 and keep CN codes), most Targets have actually completely sold out of Mario Kart 8.
Its all win win for Nintendo though, they don't really lose a ton of money giving out free digital copies of Super Mario U/Pikmin 3/Zelda HD and its spurred quite a few people to go out and buy a Wii U, including a few just on these boards (me too).