You are allowed to scratch 5 of each cards every day and they are available to buy from the Kiosks, and from users. If you buy a scratchcard directly from the Kiosks you will pay a set price, but get a random card. If you buy from a fellow Neopian you can pick which card you would like, however you will have to pay the market value. For the rarer cards this can be extremely expensive. Good Luck!