The last Kubota which my father bought was an
L2800 HST. They are nice tractors. My brother still uses it mowing and plowing snow around the property yet I still don't believe it has 450 hours on it.
What matters is that it's there when you need it.
Clean tractors are hard to find, and somebody else already mentioned that you can come down but you can't really come up in price.
With the mower I would list it at 15K or better, especially since you don't sound certain that you want to sell it. Find somebody like the poster above me and you both will walk away smiling.