But surely paypal is safe? and if i stick with a seller with near 100% reputation and no history of bad sd cards?
My apologies for showing up a little late here, but this particular quote deserves a response all of its own.
Sellers of fakes typically have 100% or near to 100% positive feedbacks, and you would be hard-pressed to find any history of selling fakes. This is because most people never realise that they've been conned until long after feedback was left, due to thinking that putting a few things on the card (or filling it with things) "to check that it works" is sufficient testing for authenticity. It isn't -
H2Testw or
F3 are the only ways (these cards are hacked to present a false size, so of course they will appear to let you fill them - these programs are the only way of verifying the true size, though). In short, eBay's feedback system is meaningless in cases like this.
If you search
SOSFakeFlash for references to PayPal, you'll find that you're very likely to have problems with them. They're very big on talk about "buyer protection", but it sounds from many reports as if they are not big on action for it in all regions (this does differ depending on the consumer protection laws of your region, though).
Anyway, everyone else has already got you covered, with regard to avoiding eBay.

I would also add to be wary of third-party sellers on large online retail sites, as well. Whilst many of them are legitimate businesses just using the sites as another outlet, fakes have been known to be sold by some sellers using this means, and if you're not familiar with the third-party sellers, it may not be worth the risk.