Hi Anil Nigam 'Bekhabar',
Buying and paying are two different steps during check out. First a buyer bids or buys (immediately the Final Value Fee is debited to the seller's account) and then if the buyer is genuine and is willing to pay for the item then only the buyer proceed further to pay for the item through PaisaPay. If the buyer prefers to pay other than PaisaPay then he/she do not continue further in the check out process.
So, choosing PaisaPay as the only payment method do not force the buyer to pay instantly during check out. It again depends on the will of the buyer to pay for the item or not.
Every seller is suffering from
Unpaid Items and eBay do not bother for it because they receive the Listing and other Featured Item Fees in advance which are never credited to the seller's account. eBay is just glad to credit the Final Value Fee after keep waiting the sellers for two weeks.