Bounties are not refundable.

https://wordpress.stackexchange.com/faq#bounty

However, good answers tend to get upvoted -- and I for one will almost *always* upvote a self-answered question where the asker put in a lot of effort to find the answer themselves.

I think you might find that you get back what you put in, both in the karmic sense and earthly reputation scores. :)