Thank you very much for the offer. You wanting to make things right is more than enough for me, so please keep the money for yourself and the key too.
I genuinely do think the price is more than fair on Steam even if it is purchasing it a second time, and I'll be buying it again now.
...in my eyes you've kept your word to me, and that means a lot. Keep up the good work developing the games, and thank you for responding to me.