Sunns have been pretty cyclical over the last several years, more up and down than most vintage gear but like almost anything that is no longer manufactured gradually edging upwards for about a decade. I think eBay is the only real barometer; you can still occasionally steal something from a private party, and conversely you will sometimes see ridiculously high asking prices, but an open auction where you can view actual sale prices is probably the only
true measure of market value.
I dont imagine you can really get hurt, its more likely a function of how long you hang on to it.
Heres one of those right place, right time stories involving a Sceptre, just to make people
really hate me
I have a Sceptre that I bought in 03, from a private party. From the (print) ad I only knew it was a Sunn guitar amp, but the asking price was so low I figured it was worth the couple hour drive into the country to check it out, I figured
I could bargain it down, dump it and maybe make a couple of shekels if it was some trashed SS combo or something.
I got lucky,
real lucky; the original owner had passed on and his widow was clearing out his toys. The Sceptre was under a sheet in the music room, a totally minty 1970 that he had bought new for a C&W band that never materialized 30+ years ago, with the factory footswitch of course. She said he only played it a few times, and that it only left the house maybe twice since he brought it home in 1970.
It certainly
looked like the truth;
Chassis still all shiny, no oxidation, just some finger prints and dust, no dings in the tolex or snags in the grill cloth. The kicker was the piece of wood over the power tranny, which was put there at the factory to keep it from shifting during shipping.
When I got it home, the original USA Tung Sol 6550s and the Mullard and Amperex novals all tested new. Its not important what I paid, but suffice to say after making a short offer which she accepted, I felt so bad that I turned around, drove a half hour back and gave her the rest of the asking price to ease my conscience.
It wasnt a desperation sale or anything; she was just selling off stuff in preparation to sell the farm. I just didnt want to lose sleep over it...
Anyway, Ive recently turned down offers
over $1000, so Im confident there is a market for nice old Sceptres.
HALP?! 
