Finally got a few minutes to get my screen shots.
First, here's the vassal list under my portrait. Note my very rich Grand Mayor. He has an income of 267.6. My burgher tax is at 35%, and he is a patrician so is allowed to keep more of his gold, lowering my take by an additional 50%. Since I'm Nomadic, opinion doesn't matter; but he has a positive opinion of me anyway. So, the total expected tax from my Grand Mayor is correctly displayed: 267.6 * .35 * .5 = 46.8
Now let's check the finance screen under the shield menu. Note that for some reason, my city tax is only 18.73. This is about 40% of the 46.8 I was expecting. This is true even though the hover-over claims that I'm receiving 46.8 from my Grand Mayor.
If your'e sharp, you'll have noticed that my Church Tax is also much lower than expected. Instead of the 14.7 advertised in the vassal list, I'm receiving only 5.94, again also 40%.
To get the above screen shots, I dumped a bunch of barons from being my vassals. Barons didn't seem to count against my vassal total; they aren't included in the count in the top right of the screen:
My total vassal breakdown after dumping all but one of my barons is:
7 Clans
1 Ecumenical Patriarch
18 Dukes
3 Counts
1 Baron
Could it be that, even though barons were not counting toward my official vassal count, they were counting towards the count when it came to calculating tax penalties? Is it possible that clans count as well? If barons and clans both count, my total vassal count would be 30, 3 over my limit. Fascinating. What happens if I liberate three clans?
After liberating three clans, note that my city and church taxes go way up! Although, not quite to 100% of what I was expecting...
But... it turns out I jumped to a hasty conclusion. I liberated a fourth clan, bringing my total (not official) vassal count down to 26, and taxes just went back to around where they were. It looks like I got suckered by another bug I've noticed: the "city taxes periodically double" bug.
So then, my last gambit for the night will be to liberate my one remaining baron and see what happens.
Well, that was unexpected. So, I will now declare CK2 finances the winner and will go to bed. This is looking more and more like it should be a bug report....