So the big trick economy wise to ensure that nobody ever has enough and always wants more? Do not just say 'You are an X level noble, you get Y income!'.
Instead put together a list of Things A Rich Person Might Want, limit the number to how much detail you want to go into. Then default people to having these things at 'Moderately Crappy'. Let them spend portions of their income to raise them, but not enough to have them all above average.
So say you are an Andoran Lady.
You have an income of (random number) 1000 Crowns a year.
You might have to think about:
Household - Spending on your servants, retainers, clothes, etc. Would effect social and political stuff and how fancy of a dress or horse you can just be assumed to have.
Guards - How many armed retainers you have, from some literal household guards, to a retinue of cavalry to a small personal army.
Alms & Welfare - How much you give back to the common people. Charitable donations, good works, sponsoring festivals, etc.
Infrastructure - How much you invest in stuff like bridges, town walls, roads, waystations, etc.
Then have all of those default to like a 2 on a 1-5 scale with 3 being 'average/acceptable' and have it cost 250 Crowns a year to raise each one by a point. Also let this theoretical noble squeeze out more money if they ratchet up taxes and/or take out loans. (or if they bring in another PC who has high Stewardship or something. Best to make the actual extra income somewhat random though and ensure the steward is in a position to seriously consider embezzling).
Make sure raising each of these things either gives beneficial shinies or ups some abstract popularity meter that has descriptions for each level saying how awesome as a ruler the PC is and loved by their populace they are, but only at the higher and very expensive levels.
I can guarantee that if you run something like this you will end up with characters who are rich but are still scrabbling desperately for every penny, trying to extort each other or going into debt.