On our front page yesterday there was an analysis of Metro's money problems. I hope you read it.

Billions of dollars have been poured into Metro. Thousands of man-hours have been expended in negotiations among officials of local jurisdictions and the federal government. Compromises have been reached on dozens of complicated policy matters.

Now, when Metro should be maturing into a cohesive unit, there is danger the unified system is about to be fragmented. Washington Post staff writer Douglas B. Feaver noted that Montgomery County is forsaking federal aid and spending $12 million of its own money for 155 new buses; Fairfax County is studying ways to replace part of its Metrobus service; Prince George's County is asking private bus companies whether they would like to replace Metrobus on some routes.

Why? Feaver says, "These events have been spurred by the costly contract Metro has with its 5,000 unionized transit workers." The starting pay for Metro's bus drivers is now $16,827. In 30 months, they qualify for a minimum of $22,432 a year, plus four guaranteed cost-of-living raises every year. "With bonuses for night work, snow days, overtime, charters and the other goodies, many take home $25,000. Last year, 142 drivers made $28,000 or more, and two drivers made more than $40,000."

A few months ago, when District Liners were up in arms about rapidly increasing food prices in the Washington area, there was great interest in union wage scales for supermarket employees. Grocery clerks get $8.50 an hour plus overtime and fringe benefits estimated to be worth an additional $5.50 an hour. Bakers and meat cutters get more.

I was flooded with letters of protest from nurses, policemen, firefighters, teachers and others who require specialized training.

The same thoughts turned up in letter after letter: "Good heavens," the teachers and nurses wrote, "My job calls for far more schooling than is needed by a person who stocks grocery shelves, and my job demands far more special training.My job carries more responsiblity. Why should my pay be so much lower than that of a grocery clerk?"

The only answer I could offer was:

It is not written on stone tablets that your pay should be lower. It just is.

Pay scales are determined by many factors in a free marketplace. One of the most important of these factors is economic muscle. Tough unions like the Teamsters tend to get the highest pay.

Try this experiment: Rank truck drivers, nurses, grocery, clerks, teachers, plumbers, firefighters, disk jockeys, policemen, bus drivers and clergymen on the basis of their value to society, the amount of schooling and training needed to do the work, or the amount of responsibility involved. Then ranked these jobs by the average amount of money made by the people who hold them. It will be evident that there is little relationship between what a job pays and the qualifications demanded of those who hold it.

Not so evident, perhaps, will be the fact that in a free marketplace things tend to right themselves over the long term. When coal becomes too costly because of wages and benefits paid to miners, other forms of energy replace coal. When Metrobus becomes too expensive because of wages and benefits paid to drivers, alternative forms of transportation replace it.

It would be a pity if Metrobus went down the tubes. It would be a pity because mass transit is the most efficient way to transport people.

But there is no room for pity in the laws of economics. Metro jobs now seem destined to decline in number. Eventually, the union's clout will also diminish.

People concerned with getting to and from work today will derive little solace form long-term economic theories, but that's how things are. There is no way to control a free marketplace.

Sometimes there are ways to hasten changes that are already in the making. But the bleached bones of many a government agency that was supposed to "control" the economy bear silent testimony to the fact that a free economy goes where it damn well pleases. CHILDREN'S HOSPITAL

Our annual fund drive for Children's Hospital has now ended. Scott Chase will begin his final report to you on Friday in this space.