It's not for -all- releases. They've just set the price of DKC Returns 3D, Animal Crossing: New Leaf, and PMD:GTI at $35, that's all. It's not like they haven't sold some 3DS games for $35 in the past either. It might be more common henceforth, but I wouldn't assume it'll be standard. Also, that price is the same at both eShop and retail.
Animal Crossing at $35 is a pretty big deal IMO. I get DKCR cause it's a port, but a new Animal Crossing game would probably sell regardless. Im personally surprised to see it at that price.
But yeah for some reason I doubt we'll see Mario games priced at that