Why are rents going to have to be higher? Because two five story buildings take up twice as much land as one ten-story building housing the same total number of people.
In a state like California, where the cost of land is often higher than the cost of what is built on the land, using twice as much land per apartment means that rents are going to have to be much higher -- perhaps twice as high or more -- to cover the additional costs created by height restrictions.
With more land being required to house the same number of people, this means that the whole metropolitan area is going to have to be larger than it would be if it could expand upward instead of just outward. More people are going to have to commute to work.
Those who impose height restrictions can ignore such things. A few blithe words about not wanting their community to look like Manhattan are usually about all the thought they give to the subject. It would never occur to them to ask the real question: How much don't you want it to look like Manhattan? How high a price are you prepared to pay?
A doubling of rent and 3 additional highway fatalities a year? A tripling of rents and 10 additional highway fatalities a year? Whatever the answer, the point is that height restrictions are not a free lunch -- whether the costs are measured in money or in lives.
A lot of people who cannot afford it are paying heavily for the ego trips of environmental zealots.