(FORTUNE Magazine) – Members of Meeting Planners International, an association of 10,000 people who plan conventions, conferences, seminars, and the like, should be toasting each other with champagne this month when they converge on Kansas City, Missouri, ^ for their own annual meeting. In 1989 corporate America paid $10 billion for various get-togethers, 37% more than in 1987. Joan Eisenstodt, a Washington, D.C., planner whose clients have included Digital Equipment and National Geographic, says senior managers seldom understand how much money a professional consultant can save. Says she: ''When a company goes shopping for a $300,000 computer, every vice president wants to weigh in. Their convention probably costs more, but they think any secretary can handle it.'' Even professionals admit that they themselves sometimes err. MPI's own meeting last year was brought briefly to an unscheduled halt just as the group prepared to hear a keynote speech: The band was still, the audience hushed, and the curtain rose -- only to hoist the drummer's cymbals ten feet into the air.