Since 1973, Israel has cost the United States about $1.6 trillion. If divided by today's population, that is more than $5,700 per person. This is an estimate by Thomas Stauffer, a consulting economist in Washington. For decades, his analyses of the Middle East scene have made him a frequent thorn in the side of the Israel lobby. For the first time in many years, Mr. Stauffer has tallied the total cost to the US of its backing of Israel in its drawn-out, violent dispute with the Palestinians. So far, he figures, the bill adds up to more than twice the cost of the Vietnam War.