If I understand you:
You made an offer on an item.
The seller did not accept your offer and sold the item to someone else.
If that is the situation, no, you don't have to pay for something you will not recieve.
But:
If you made an offer that was accepted, then you do have to pay, even if you found a better deal.
The alternative is losing an Unpaid Item Dispute and getting a Strike on your account which will make it harder to bid on eBay.
