And how was it stored when not in use? Inside or out? Paint faded? Tires checked? Seat cracked?
And how was it cared for during those hours and years? Oil changed? Greased? Zerks looking like they seal well? Scratched and dented? Dirt and/or manure left hanging here and there prior to the dealer getting it? Look for stains on the paint. Hoses and lines in good shape? Battery clean or showing signs of sulfate buildup on the terminals? Air filter clean? Just replaced? Radiator screen? Fuel filter bowl?
Any signs of touch up paint? Nuts and bolts look like they've been improperly wrenched? Tires loaded? Seat belt look like it was used?
Is the brush mower a brand name like Bush Hog or Kubota? Is it the same age as the tractor? Is it something the tractor can fully lift, or too heavy, like my Huskee? Does the gearbox leak? Have you run it? Have you tried out the lift?
Look for signs of abuse or lack of care. With those few hours, there should be essentially none. The thing should look almost new, with some paint wear on the bucket and foot contact areas. Barring that, the price seems in the ballpark. Check E-bay for similar machines and see what prices are being offered or sought. Good luck.