hey I hate to be the bearer of bad news but someone has to do it - I don't see anyone giving you more than the pawnshop for this. To start, rapiers are not very good as a weapon base. Also, few people are looking for anything +10 b/c only 5 levels later you can use +20 so it's extremely niche.
The treasure system in GS mashes together a bunch of attributes and often you get something like this that's not a useful combination and just has to go to the pawn shop to die.