That should *never* be the case as a casher. Sounds like you might have a tech problem. You want at the very least 10 points per acre each of bus/res, and as the reset progresses that should be more like 30+

Bus/res are multiplicative. ie
Both at 120% gives overall x1.42 modifier to income
Both at 140% gives overall x1.96 modifier to income
Both at 160% gives overall x2.56 modifier to income
Both at 180% gives overall x3.24 modifier to income

going to 180% is not worth it though but you can see how high 170s will still give you almost 3x income.