The way the administration's economist-turned-chief diplomat figures it, the U.S. search for peace in the Middle East is a bargain item costing only about half as much as Americans spend each year on flowers and potted plants.

Secretary of State George P. Shultz took this unusual approach to foreign policy activity in an address yesterday to the Southern Center for International Studies in Atlanta.

According to Shultz, it will cost each U.S. citizen $12.35 in the next fiscal year for "building peace in the Middle East," $3.84 for the Caribbean Basin, $3.15 for "building secure food supplies," 92 cents for curbing population growth and 77 cents to aid Turkey.

By comparison, he said, Americans spend $104 per person a year for television and radio sets, $35 per person for barbershops and beauty parlors and $21 each for flowers and potted plants.

Figures later made available by the State Department, however, suggest that some of Shultz' calculations are incomplete and one is incorrect.

His figure for the Middle East includes military and economic aid, a total of $2.8 billion. But it omits $2.1 billion in U.S. military sales credits. Shultz' Mideast calculation also does not include the cost of maintaining U.S. military forces in the Sinai or Lebanon.

A mistake in calculation resulted in Shultz' statement that aid to Turkey will cost each American 77 cents. The correct figure, allocated among 230 million Americans, is $1.77, according to State officials.

The department explained that the Caribbean Basin figure cited by Shultz includes U.S. military and economic aid in the Caribbean and Central America. The figure for securing food supplies is the cost of bilateral U.S. aid to other nations for their agriculture and rural development. The population figure is the total of U.S. assistance to population control programs in 27 countries.