If the tractor is in good running condition, undercarriage not worn out and misrepresented, (components need to be measured to determine actual wear/condition) and if it has an oil clutch, they are worth $4000 or better if in good condition. 9U was a reliable, well built, popular tractor in its day.
Other things to consider about one of these to see if there are any serious or impending problems are as follows:
1.) you can pry against the track sprocket to see if its loose on the dead axle, hopefully not run a lot of hours like that if so.
2.) you can dip a magnet into the final drive housing to see if metal fines, particulates or flakes are present to see if there is a bearing going to fail or signs of repairs needed to the final drives, which require special tooling and expensive parts
3.) inspect the tractor for hard abuse excess wear and poorly made repairs, like suspect welds in places like track frames or housings.
Just some idea as to see if there are any other issues, I assume the clutches replaced were steering clutches,brakes, if a dry clutch tractor, they were just becoming standard around '52, could make the tractor worth a little less, dry clutch requires more service and adjusting, gives less service life than an oil bath or wet clutch does. There was a field kit for these in those days to retrofit an early tractor, so sometimes you find ones that were dry type from the factory, but change over later, hopefully this is of some help.