Blast chillers are obviously not yet a 'common household item' so could it just be that the reason there are so many for sale (at such a significantly reduced price compared to a new one) is merely because they have been owned by restaurants that have failed ... which unfortunately is quite a common phenomena. Many don't start restaurants on a shoestring, especially the kind of restaurants that would equip themselves with a blast chiller, so they may have purchased new, used for only a year or so (I think many fail within that short timeframe) and have to liquidate quickly at the end.
If there were already a few on the market at 3 grand (for whatever the reason that price was set), I am not sure they could justify trying to unload at a much higher price. It could actually be that the fact there are so many of the same brand is that they bought that brand because they heard it was good (or a very good value for the money) - and maybe it really is. Or they bought used at a slightly higher price - the 'history' of a particular machine (how many previous owners, how long was it actually used in service) could be more important than the brand - and now need to sell at whatever they can get for it.
I might want to ask other restaurant owners what kind of chiller they have and how reliable/good theirs has been before consulting repair people. What made them decide to get that particular brand, whatever their machine may be.
No real experience here - just questions I would be asking myself if I was in the market for an expensive appliance like that.