Employes who took long coffee breaks, drank three-martini lunches or otherwise goofed off on company time cost their employers a whooping $98 billion in 1980, according to a study by a New York personnel recruiting firm. The survey by Robert Half Inc. revealed that what the firm calls "time theft" averaged four hours and five minutes a week per employe in the United States -- time valued at $6.66 per hour on the average. Half thinks that the time-loss figure may be conservative, but admits the survey was based on employers' estimates of how much company time workers wasted. Robert Half, head of the firm, characterized extreme cases of time theft as "stealing" at a time when the nation's leaders are concerned about America's loss of its competitive edge and the deterioration of the work ethic. Pointing up the scope of management losses because workers dawdle and daydream, the survey notes by comparison that embezzlement, arson and other white-collar crimes cost U.S. companies $40 billion last year. Half is no Scrooge who suggests employes be chained to their desks or work stations. "If someone takes time out to chat with his colleague, is that a time theft? I say no. Neither is a trip to the water cooler," Half said in an interview. "Nothing is a time theft unless it's excessive.A personal phone call is not a time theft unless it's excessive." By Half's standards, the ironworker on the fifth floor of a high-rise under construction who emits a wolf whistle because he admires the structrual attributes of a passing woman is not guilty of time theft. But if his whistle halts the work of 20 other ironworkers whose attention is then riveted, so to speak, on the passerby, and if they all watch her until she passes from view, that may be more than a borderline case. There are obvious offenders familiar to fellow employes who are more conscientious or chisel just a little, however. They include the file clerk who spends half an hour doing her nails; the fellow who spends an hour reading the morning paper; the crossword-puzzle addict; the sharks in those stockroom gin rummy games; the restroom loiterer, and the TV fanatic who gives fellow workers a long account of last night's "Dallas" episode. "One of the biggest thefts is loafing to create overtime later. If somebody figuratively has his feet on the desk all day and then puts in for three hours' overtime, that's stealing. And it happens," Half said. Within limits, Half subscribes to the theory that all work and no distractions not only make Jack and Jill dull people, but also maybe less productive. "We allow for relaxation at work. You can't just work, work, work. . . . You've got to look up once in a while, take a coffee break. You've got to do these things or you'll go out of your mind," he said.