Yep, priced about double too much.
You didnt mention rebuild, So I am just assuming it was a paint job restore. Sure it makes a tractor look good, but dont make it run any better. And depending on the quality of the person doing the paint would say alot. I have seen alot of crappy paint jobs on these tractors, and usually the wrong color to add insult to injury.
There are a ton of other things that they may or may not have addressed when "restoring". The front axle pivots, and axle to radius rod connections tend to get sloppy. Were these addressed? Is it still 6v or is it a hacked up mount of an alternator for 12v conversion? or is it a 12v done right with clean wiring and nice bracket?
How do the rims and tires look?
3PH arms....how loose are the balls? like they are ready to fall out? or did they get repaired/replaced.
Battery tray? Rotted out and painted over? or fixed right?
There is alot that goes into an actual "restore". If it was done properly, and with an engine overhaul, $3500 would be about top of the mark and he probably isnt out of line asking $4100. But a restore done right, I'd say maybe 1 in 25 tractors that claim to be "restored" are done right. The rest are different levels of quality, but usually it involves taking a runner that someone paid $800, Degreasing/powerwashing, and slapping on some fresh paint and calling it restored.