The cost of public prominence has tended to be higher.

Also, he said, the cost of any new technique tends to drop rapidly as more companies compete for the business.

The Mayor's move showed how the cost of borrowing tends to crowd out other spending.

In a bigger, more diverse group, the extra costs of care for some people tend to average out.

"History has shown that when health care is covered by insurance, whether public or private, its cost tends to rise rapidly," he said.

Once again these costs tend not to be strictly linear in reality.

While the energy solar cells provide is free, the cost of materials and installation tend to be high.

"Most of the buyers are individuals, and the cost tends to be low."

The costs will thus tend to be passed on to investors.

Because these items are mass produced, costs tend to be lower than for specialized military technology.