Well, I did some guesstimates of the nobility here. I did some guesstimates on House Lannister’s income here and here. 

The Great Houses probably all have incomes in the hundreds of thousands, given how much land they’re drawing taxes from, peaking at House Lannister’s million a year in gold. 

In terms of a relative ranking of  incomes, I’d say

Tier 1: Lannisters ≥ Tyrells. Obviously, this depends on agricultural prices at the time, and arguably demand for gold as well.

Tier 2: Arryns. The Vale is noted to be as equally fertile as the Reach, if not as big, and they’ve got a significant presence in Narrow Sea trade. 

Tier 3: Starks, Baratheons, and Martells? Here’s where things get really hard to figure out. The North is immense, but not the most populated and the soil isn’t the best. However, it’s still arable land, and more importantly the Starks have access to valuable commodities – timber, wool, and silver. Likewise, much of Dorne isn’t arable and therefore the population isn’t very high, but the Dornish do export wines, niche agricultural commodities (peppers, citrus fruits, olive oil), and silks and satins. So I’d probably put the Martells ahead of the Starks, but I’m not sure whether it’s a tier’s worth of difference. The Baratheons probably fall somewhere in the middle – their land is a lot more productive, but they have a relatively small amount of it after the loss of the Crownlands, although they do have amber to sell (not sure how big of a market that is, tho). 

Tier 3.5: Tullys. This is almost entirely a product of political disorganization. The Riverlands are large, incredibly fertile, and draw a lot of trade due to their central location. However, the Riverlands are not well-developed: they don’t have any cities, their road network could be much more developed, they need more bridges, and it’s absolutely criminal that no one’s built a canal linking the Blue Fork to Ironman’s Bay to boost trade. Likewise, I don’t think the Tullys are as good at getting taxes out of their nobles as the other Great Houses, so there’s a lot of wealth in the Riverlands that doesn’t make it to Riverrun. If the Riverlands were better organized, I’d put them easily in Tier 2. 

Tier 4: The Greyjoys. The Ironborn have the smallest population and the poorest productivity of soil. Trade is diminished by the Ironborn’s hatred of “the gold price,” and the fact that iron isn’t that great a commodity to trade. Contrary to what you might think, piracy isn’t that great an income-generator: at best, you’re grabbing a percentage of the trade everyone else is making, it’s high-risk and income is intermittent, etc.