A lot of people get non-Kubota filters (at least for oil and transmission - not sure about fuel) and save a fair amount of $$$. I am lazy and just get them from my dealer - I've looked at TractorSmart and they are pretty reasonable but my dealer doesn't mark up parts too much. I pay about the same there as I would online for most stuff. It does mean I have to drive over there, but it is a short trip for me.
You might check out the "lubricants" forum, though, and search for filters. There are less expensive (and potentially better filters - the grade of the elements is discussed in great detail in some threads /forums/images/graemlins/smile.gif) options.
And then you can start worrying about the type of oil and hydraulic fluid to use /forums/images/graemlins/laugh.gif... That is a whole other area to worry about /forums/images/graemlins/wink.gif...