its worth what someone will pay.
i sold my A4000s off last year, and my B2000 back in 2005. In a couple of years time I'll be trying to buy them back, and if the owner wants more than he paid... so what.
I'm selling off my retro stuff as I've had it for years, and still get the teary eyes when I fire up Galaxians on the TRS-80, but I rarely use it anymore even for that memory lane trip. Its whatever it is worth.
Sure, there is always emulation, but it aint the same. And yeah, it sticks in the craw someone trying to sell something at an "inflated" price.. but lets be honest, if you had the disposable funds, what would you pay???