I second keeping an eye out on FB Marketplace or similar. I picked one up for free that way!
I also put in a vote for a spiral machine (vs. comb).
Initially, I bought a machine a couple years ago (out-of-pocket) and I used it a lot for school, customizing my own school planner, and robotics team tasks. I'm at a small private school -- last year the kids spiral-bound our school planners and yearbooks, to save money and also because they love the spiral machine! Then, this fall, as I mentioned, I picked one up for free. (Which means mine can now live at home, where it belongs.)
I purchased the MAKEASY Coil Spiral Binding Machine, which runs around $100.
C. Mytko