Wii Points cards are priced (here in the U.S.) at $20 for 2000 points. Nintendo gets all the money; there is no profit left for the seller. You're probably thinking, "hey, they're being greedy!" Actually, not quite. Apple does the same with iTunes Music Store cards. Possibly Microsoft with the XBM cards, as well. So how does this all work out? Well, if you get a customer to walk into the store and buy a card, then there's a possibility (s)he may buy other products within the place. That's the hope anyhow. Redemption cards are really provided at a convenience, that's all. Some stores do mark them up to make profit though.
Also, Euros =/= USD, etc. You'd be surprised, but Japan is actually paying LESS than the U.S.A. for points. Historically, Japan always pays more for its games, but that's the market. Anyhow, I'm not bickering.