You could always edit or reply to your original thread since it covers the same topic (and pretty much the same machines).
An Atari ST depends on what model and what accessories you want with it. I've seen them go for $20 (machine only, no psu, mouse or anything else) up to several hundred.
Again, the Compaq Portable depends o. Which model and how it's configured. A quick eBay search suggests about $100 shipped for either a Portable or Portable III.
I don't know anything about the IBM gear and the NeXT stuff tends to go for some serious coin.