On the surface, would say that tractor (as a compact not a full size model) has used up about half its useful life without some major expense in future. What does tire tread look like? They are getting pricey. Works out to about several hours a week, every week for last ten years. Private individual or business? Would maybe go max offer of around 50% new. If same hours but more like 20 yrs old can figure it had a cushy life. But at 10, that rig has seen some long hour days probably.
If a rental place would consider all the noobs who probably ran it and discount it according. They did dumb things just trying to learn how to operate it. I did too the first few yrs owning a tractor. But new operators every week are hard on stuff. Lent my rig out to half dozen friends in the early days. Think 5 outta 6 times something happened even if they did fix it. Bent my back blade mounting, broke the steering coupling, power washed the chit outta the dash and now couple gauges don't work or erratic. Hey what are friends for? Lol. But you get the point. Constant new learners are hard on stuff and discount your offer if that is true for this rig.
Kubotas are good rigs tho. No problem with used if fair priced.