One of our member, Kev, has posted this question as a comment of the Fet/10 He article:
Hello everyone, i was just wondering, if i have one of these used that i received from a relative, how much would it be worth? in good condition, no nicks or scratches, just used.

I would say that the normal price, as seen on eBay, is about $1.000 to $1.200 for a silver Fet/10 He.

If it is a black version, more difficult to find, it could rise up to $1.300, but curiously it seems that more people are looking for a silver version... Maybe because it is a vintage preamp and they prefer it in a silver version, who knows...