I don't know for sure if Kioti follows the same type of hydraulic filter requirements as does Scag mowers, for instance, but Scag say to NEVER use an automotive type filter for the hydraulic filter replacement on their mowers.
I suspect the filter level of the automotive and tractor professional mowers is somewhat different if not completely different, hence the big $ difference. I sure wouldn't want to use a cheap quality filter on my tractor and have something go wrong. BTW, I'm not saying the Napa filter is junk, I do not have anything to make an apples to apples comparison from- and unfortunately I think the filter manufacturers like it that way- especially companies that sell their own brand of high priced filters- like Kioti, Deere, etc.
Anyone know for sure- facts vs. conjecture?