The problem with registars like GoDaddy, DynaDot, Snapnames, etc. is that virtually anyone can bid, and they treat a $50K domain auction win with the same business processes as a $5/month hosting plan.
Into the Cart it goes, they have XX days to pay, no requirement for a CC or other payment method, lax collections, etc., so by the time the deadbeat hasn't paid, there is little time left to resell or reauction it to anyone else.
That's why so many unpaid domains end up expiring and get caught by drop-catchers, and as I've said before, it wouldn't surprise me that some "outside players" are actually manipulating these expired auctions.
Bid ultra-high, win, delay XX days until the transaction auto-defaults, wait for it to expire, then try to catch it and make $$$. Where there is money to be made, there are always scams being run.