To all sellers using PayPal, beware - I've just found out (actually, it was used on me) that there is an exploit available, which lets users change the price of your products before paying. Everything else is just like a normal sale - they use the buy now button, purchase the product for $0.01 or so, and can then download with returning to your website. I don't know if it allowed to post this link, but if it is, I'll post it later so you can know what to watch out for. Just remember, notice the item price on the invoice - I was stupid enough not to notice that
I had the issue with payloadz. but they sent me a mail saying that the transaction amount does not match and what they should do. I declined the transaction and refunded the money