If you check KEH prices, you'll find manual Nikon bodies for about what you'll find Pentax K1000, etc., and with people dumping their manual lenses, the lens selection is both wider and less expensive. A cleaned FG/FM/FM2 or even FM10 will do you quite nicely, and it's hard to beat the lens selection. Fast normals are ~100, and if you consider the older pre-AI Nikkormats (you'll need a hand-held meter), you can get the non-AI lenses even cheaper.

Depressingly, I see that the Fs, on the other hand, are going back up in price.

Any Canon FD or Olympus OM defenders care to offer a take on their current viability? Nothing wrong with the Pentaxes, but there are a lot of good choices out there today, which have suddenly become affordable.