When you place a bid, the platform checks the balance of your wallet. Your bid will only be accepted if your balance is equal to or greater than the amount of WETH you are bidding. If it isn’t, the bid will be declined. If accepted, your funds (equal to your bid) are not put on hold by NFT STARS but you do give NFT STARS permission to perform a transaction. The platform subsequently creates a pending order. That's why collectors do not pay any fees and can place multiple bids.