I can't believe your BX2230 costs are much different from my BX1880 cost so here's my story.
Being a "new" tractor owner when I did the 50 hr. service I did what you want to do, searched high and low and bought stuff from local stores and Amazon thinking I can get it cheaper and save a few $.
This March (with 300 hrs. on the BX) I bought everything from the local Kubota dealer. Got all OEM stuff in one place at one time, no running from store to store or waiting around for delivery of the wrong (happened) or missing item(s). Could I have saved a few dollars? Maybe, but my time is worth more than that...and I'm retired and have plenty of time.
Motor oil filter ($12.80) and fuel filters ($8.70 each) were no more than any 3rd party seller. You can probably get cheaper "equivalent" filters but how much are you really saving and are they really "equivalent"? Maybe, maybe not. I've never bought a 3rd party hyd. filter but the OEM one was $22.62, reasonable considering the size and psi rating. The air filter ($16.88) I thought was reasonable also.
Kubota UDT2 was $30.15 / gal and the 10W30 Kubota diesel engine oil was $26.58 / gal. also at the Kubota dealer, which was less expensive than where I was looking on-line.
JM2C.