Every once in a while, my city income dips from like $1,250 to $32 Dollars P/H. Then people get mad for high taxes, and move out... What is this, Why is this, and how to stop it?
It's hard to say why your city income dips since it is composed from many sources.
Here's a few sources to check.
RCI: upgrades, move outs, or lack of basic services (power, water, sewer, garbage). I gathered tax data for many RCI buildings and found income per hour for each building is a flat amount * tax rate. However, this amount can be reduced when basic services are missing.
Megatower apartments: income per hour is based on occupancy which can vary.
Tourism, Casinos, megatower malls and megatower offices: income per hour is based on utilization, which can vary to extremes. Specifically, these income sources periodically reset to zero and then build up based on utilization after the reset.
Importing/Exporting: when deliveries are made varies.
If you don't have enough income overall, RCI is a great place to go because of its stability. Just add more RCI buildings and keep them down at medium density to spread them out and maximize taxIncome/serviceCosts.
If you have high taxes people move out. If people move out you collect less from taxes (of course).
This explains the income variation.
You need to balance happiness with taxes. You can raise them for a while in crisis then lower them back. I've noticed that you can go to 12% for poor, 11% for medium and 10% for rich and not suffer major penalties.
In order to progress, I suggest not using taxes as your main income. For example you could rely on industry and export. The income from taxes may go negative, but the exports compensate.
The worst thing that can actually happen to you is for all the people to leave (this will lead to high crime rate, fires, abandoned buildings etc.), so you should take care of that.