Four days after a sale, you can and should file an unpaid item dispute and then close it 4 days later if you still haven't been paid. You can and should add any non payer to your blocked bidders list before or after filing the unpaid item dispute. You should also set your buyer requirements in My Ebay to block bidders with 2 or more unpaid item strikes in the past 12 months.
Non paying buyers deserve unpaid item strikes.