Sonny Crockett and the BrenTen - YouTube
What caliber is it? .45 or 10mm? The Bren Ten definitely has a cult following but as you said it was sabotaged by morons running the company and contracting with a vendor for mags that didn't have the ability to make functional ones (fine choice there...) and went under in like 3 years. The Bren Ten is more or less a copy of a CZ, I don't know what it is worth but I do know it is a LOT. I've heard of the magazines alone going for like $200. That is on the list of historically significant from pop culture guns I plan to acquire, the Walther PPK (an old one not a new one) being another.
My semi informed guess is that he can get several thousand for the Bren Ten, but I wouldn't sell it personally.