What do you think a circulated BSW would go for if I were to try and sell?
IMO: Charlton puts a VF BSW$20 at $40- so maybe that (or marginally more)? It's hard to say because the market seems really hot with auctions but pretty dead elsewhere (so it would depend how you sell it/buyer's premiums, etc).
I am not interested in selling,
IMO: that's good because you'll never get what its truly worth (as far as how rare it is).
No one seems to acknowledge the fact that this is one heck of a rare note (like the M/C FTH $10, $50 AMK, $100 EKZ) other than a few SNDB contributors who've scanned countless bundles/bricks and have come up empty handed.
But having said that: It likely prudent since everybody thought the M/C HBG $5 was quite rare and then BOC suddenly dumped about a million well after its release (after a few were discovered). Anybody who bought one of those going by the low # reported got "burned." Frontiers are still being released so most collectors hold the faint hope that they'll come across one of these. It would be best to sell once a new series has been released and the note is firmly established as a rarity.