yeah npb is an annoying problem on ebay. with ebay's rules, no buyer/bidder takes ebay seriously. so if you don't pay, you get a "strike." big deal. 3 strikes, you're banned. so what? just create another account.
ebay should force users to submit bank account information/credit card information upon sign up and once someone bids and wins an auction, ebay/paypal should auto debit/charge the user's account. if they don't have enough balance/credit, then they'll have to face overdraft charges and over limit fees. sellers shouldn't have to wait for the buyer to gather enough funds to pay for an item or when the buyer feels like paying. there has to be real consequences of not paying, not just superficial strikes. impose a fee on the buyer if they do not pay, at least to cover the seller listing fees. it's sad that money is the only factor that'll drive people to act and respond. buyers need to realize this isn't a game.
i understand ebay is trying to preserve a "traditional" auction process where the highest bidder pays later; however, sellers are not protected legally at all if the highest bidder does not pay, unlike traditional auctions. ebay just preaches about bidding being a legal contract, blah, blah, but it really isn't.