I went to a local (Virginia) ham radio swap meet last month, one of the vendors in the parking lot area had a crate with 6 or so Model M's. Wanted $35 each for them, if I wanted a cable that would be extra*. (Bear in mind, these were completely grubby units, looked like they'd been stored in a barn.)
Judging from Ebay sales and search terms, I think there's a lot of price inflation going on, with some really poor-quality boards posted with high set prices, maybe just to seed the market. With Unicomp selling new models (in black! with USB connections!) for $80-$100, I hope prices will stabilize somewhat as buyers do some research. It's pretty chaotic to see what appear to be identical models on offer for $0.99 and $239.00, and every other seller listing their keyboards as "Vintage Clicky" models.
(*Told me; "...people who want these keyboards usually have the cable to connect it to their PC." And then offered to sell me the cable for another $10.)