That difference as when I go thru one that was for resell I check everything and actually use the mower myself for at least a couple three acre cuttings. I don't just fix the obvious things. Even the mower I repair get a good field test when I am thru as the customer will not tell you about every problem.
Beside most repairs this year are running in the $300 to $700 range. I got one out there that running close $2500 as it getting a short block Kohler engine. Owner changed his oil and forget the most important part of the oil change.