I know I will probably get alot of 'it depends' in response to this
question, but I guess I'm curious when a flight school charges a
student $25/hr for flight instruction, what chunk of that actually
goes to the CFI?

And realistically your average CFI is not flying all the time. Figure
in weather delays, ground school, etc - what would a 'good' yearly
salary for a full-time, low-hour CFI be?