well no one wants donuts, no matter how low I set the price 🙂 But I get Homer and Wiggum is in another game.
Most money still come from selling things. When I need money I stop expanding and sell everything. 40k with 50000 people is matter of day or two. Not that hard. And if market actually worked it would be much more. You are not supposed to build new houses. You need to control your level and build houses only after you have covered all services for them.
Taxes are worthless. They won't rise with population increase. 50k -> 150k means like another 2k from taxes.
So.. education/transportation do really nothing in this area. It just raise land value to the point where better buildings are built (but same people in those houses and as said tax increase from 50% bonus is neglectable).