I put a Sunn 1000s with a master volume mod :-/ on layaway for $800. It's on a hold until next month. The thing is heavy as shit. Sounds great. Wish it didn't have a master volume. I'm also probably going to get a Sunn 2x15 cab (non JBL) for $140 because why not (not the one that originally came with this amp). I think the price is a bit high but these things don't pop up very often. I may end up getting rid of my Traynor YSR-1 as a result and probably/definitely will get rid of my Avatar 2x12 now (wanted a cab with wheels anyway).
$800 for a 1000s is kind of a good deal, provided it's in good shape.
The last one I saw went for $1000. Solarus and Sonaros generally go for $600 but those are much more common.