Also check the Kumar Bros auctions, they specialize in aftermarket parts and overhaul kits for Kubota engines and are probably sourcing parts and filters from the same overseas sources as Kubota uses as the parts are very close to identical.
For a while I was getting oil filters made in the USA from Kubota USA at my dealer but now the sourcing has switched to China, the only difference between the Kubota parts and some of the other ones is the parts sticker with the hologram seal.
As for the Ebay dealer discounts, if they buy the bulk packs for dealer service use, the parts are cheaper, overall Kubota is usally either using Donaldson , Fleetguard or other large manufacturer for the air filter systems, a few of my machines have Donaldson air filter housings
Paying about $40 for a reinforced tier 4 air filter is getting stupid, this tier 4 tractor parts cost run up is ridiculous.
David