Struck by a late-afternoon attack of the munchies, a worker scurries to the company break room, drops a dollar's change into vending machines and walks out with a candy bar and a can of pop.

The scenario is repeated millions of times each day, evidenced by the estimated $24.5 billion U.S. consumers spent in product vending machines last year.But the numbers are deceiving. Nationwide, the business of selling candy, cold pop and coffee via vending machines netted a mere 3.3 percent pre-tax profit in 1989, according to a study conducted by the international accounting firm of Price Waterhouse.

Yet, advertisements tout vending routes as "lucrative" business opportunies, jobs that enable one to work part time and retire in less than 10 years.

Not so, says Bruce Goodmansen of Provo, who responded to a similar ad about a year ago.

His vending machines have been vandalized repeatedly, and he fears he will be unable to obtain replacement parts.

Vending has gone bust in many of the businesses and shops on his route, so he has had to find new locations for nearly half of the 50 machines he obtained when started business a year ago, Goodmansen said. "People call me up and say `We don't want your machine anymore,' " he said.

The biggest disappointment, however, has been the vast difference between Good-mansen's actual income and the high salary promised in the advertising pitch.

"They told me I could earn $50 to $200 an hour. There's no way I can do that. Well, maybe if I had four machines at one place that were completely empty. It would be about $25 a machine. But that doesn't happen," Goodmansen said.

His has been a costly lesson, one he will not repeat. "No way. It's in litigation now," he said.

Dennis Johnson, owner of Page Vending Co. of Salt Lake City, is often approached by people like Goodmansen who are in over their heads financially in a vending business gone bad and want someone to purchase their machines and inventory.

"Ninety-nine percent lose their money doing that. They end up paying three or four times what the machine is worth. They're not the kind of machine I would want to buy," Johnson said, shaking his head.

What the ads don't tell entrepreneurs is that vending is a demanding service business. The hours are long and there's not a lot of money to be made.

"A short day for me is 12 hours. You have to be available 24 hours a day, seven days a week, including holidays, to service the machines. You really work for your money. It's not an easy business," Johnson said.

Page Vending Co. has about 500 accounts and Johnson and his staff of 10 people service 800 machines. Johnson carries a cellular phone and dispatches his employees via two-way radio.

"The difference between vending companies is service. That's really all we can offer that's different than anyone else. We all basically use the same products. Some give service and some don't, that's the difference," Johnson said.

Like any other consumer businesses, the product line is driven by trends. People are eating healthier foods and fewer are smoking.

To meet the changing needs, vendors sell salads, cold sandwiches and fresh fruit by machine. However, the machines require more maintenance and the shelf life of a salad or sandwich is short. "We really have to watch that because of liabilities. You don't want to feed someone a bad sandwich," Johnson said.

Light chips and pastries also have become more popular as Americans attempt to curb their fat intake.

Cigarette machines have become passe because fewer people are smoking and Utah legislation has restricted the use of tobacco vending machines.

"I had to pull 60 vending machines out. That took a real knife to my business," Johnson said.

But a number of entrepreneurs have attempted to rescue cigarette machines from the scrap heap by revamping them to vend items ranging from popcorn to sanitary napkins.

A Salt Lake vendor had some discarded cigarette machines painted pink in hopes of selling small bottles of perfume from them. But the venture was not successful.

But Johnson is optimistic other items will replace the cigarette sales. The industry has endured many changes since the first vending machines were developed by ancient Egyptians about 215 B.C. to dispense holy water.

The user dropped a coin into a slot, which triggered a set of weights and levers, which splashed out a small portion of holy water, said David Stone, spokesman for the National Automatic Merchandising Association.

Since then, vending machines have been used to sell everything from pencils to microwave popcorn. And Stone said inventors are attempting to develop machines that will serve french fries cooked in their own packages.

For now, Johnson will rely on the staples of the vending business to meet his payroll. His best seller? "Snickers," he said without hesitation. "Well, Reese's Cups are a close second."