If you've ever seen the Animal Crossing e-reader cards (Gamecube time period) you'll be reminded of those when looking at these. They are very similar.
I believe- but may be incorrect- that in the U.S. these cards will come in 5 packs. I'm not sure what MSRP will be. The cards I got came from AmiAmi, it was about $15 for five packs of three.
That being said, if you're thinking about ordering some Japanese Amiibo cards I'd actually highly advise against it. I love the cards, but the price is too high for what you're getting. Try to avoid sites like Playasia *though if you must, it is the cheapest* where the cost of the cards is about $6 a pack and you're only getting one pack, it'll make you feel like you're getting ripped off.
Each pack contains an assortment of random "regular" cards and one special "holographic" card. The card holder (looks like a little book) is not included with the cards but is fairly cheap to purchase on its own. It's really cute, and absolutely perfect to store a small number of cards in!
I have not tried the cards yet, but will update when I do! Japanese cards should still be compatible with any region consoles.
Really I'm quite happy with them! I expect that the U.S. release of these will cause me to go basically broke.