There seem to be a lot of used ones available.
Might be a clue.

Hi, I was just passing thru and saw this question.
I have used a Wood Mizer portable sawmill.
Place I used to work at had one.

Unless you plan on doing a LOT of truly custom milling,
then save your money.
You won't be able to produce lumber cheaper than what you can buy it for.
And it is ungodly hard and dirty work.

I wanted one of these till I used one.
I have been thoroughly cured of that idea.

Pooh Bear