By now, yes.
There is a new option to cancel an inadvertant purchase, but you have to act within a few minutes.
Contact the seller, explain the problem and apologize. Ask for a Mutual Cancellation.
When the request for an MC arrives (and it is voluntary on the part of the seller) agree immediately.
He gets his fees back (about 20% of the cost of the item + the cost of shipping) and both of you are released from the transaction.