PayPal and STRIPE. Some people think PayPal is too restrictive. STRIPE allows more cards.
PayPal is "pro business" because they take Draconian action whenever anybody gets uppity about a transaction. Everybody learns really fast just to take a small loss and not complain. Anybody with a PayPal account is going to behave themselves, or they will get their account frozen for 6 months - hey, nothing personal, they'll do that to anybody. STRIPE has no such motivations. STRIPE is more like a minimum wage cashier at WalMart.
We take aggressive measures to not profit from the shipping of the products. Most products go USPS first class, or USPS Priority when that gets within spitting distance of first class. Our goal is to pocket no more than 45 cents for handling/keypunching, above the actual cost of packaging materials and postage. We strive to minimize postage, too.
When a customer pays too much shipping, we reduce the charge to the right amount (actual cost plus 0-45 cents) at the same time we ship it. When Red Eye refunds some excess postage, it turns into a refund that seemingly comes out of nowhere: No identification of transaction, just POOF somebody sent you some money. Cheap store = cheap functionality.
International purchases present a problem to Red Eye, because eCrater does not give a hoot whether they get postage right. eCrater has a corporate goal of selling only downloadable software. If you are outside of the US, you need to send your list of items to order to email@example.com. What happens then is I send you and invoice for the parts and the shipping. You don't need a PayPal account to pay a PayPal invoice, but they might get all uppity about your credit card. If this happens, we can send a STRIPE invoice instead.