No mods and careful use on a box stock gun in nice shape and blue label was not an option.... up to $440 plus shipping or transfer. If I could buy blue label, probably $400. Anything useful added to it, add accessory cost at about a 50% depreciation rate. I just sold one here for a little less than that.
These things don't really wear out. I have one with 35-40k rounds that is functionally even nicer than a new one. Trigger doesn't really start to wear in until 5-6k rounds.
A lot of used 34s were gaming guns...watch for breech face pitting from shitty reloads or frame battering from recoil springs that were too light. The other thing that comes from glock frame battering is the locking block pin loosening.