Yes, you have answered your own question, they are allowed to do it again and again.  eBay don't seem to have the will or the want to restrict non payers as effectively they are buyers and buyers mean money for eBay at any cost.  

Open an Unpaid Item Dispute after four days if payment is not received, the buyer then has another four days to pay for their purchase.  If that doesn't happen then close your Unpaid Dispute (it has to be four days to the second before you can do that) and then you get your fees back.

Make sure you put that buyer on you Blocked Bidder List  and they shouldn't be able to buy from you again.  Also make sure you set your Seller Preferences to exclude buyers who have received two strikes in the past twelve months and this will weed out some more of those non payers from buying from you.  Hope that helps.