I got my 110 for $25 and the older model the 500 when it was called that for $20. The LFS near me sells it for $60 everyday. So yea, I would not spend more than $30 on a used one even if I was desperate.
I also bought a Rena XP3 cannister filter for 15 bucks without the tubing and intake and outake things. But I got that for 4 bucks somewhere else.
Yea, buying used is a way to go.