The Pentagon is not the only outfit that pays $400 for hammers.

I know. I bought one last week.

It wasn't a hammer, actually, it was an on/off switch. And it only cost $331.70. Plus installation.

This particular electrical switch was supposed to spend its working life inside the door of my car, turning on and off the electric motor that moves the car window up and down.

But the switch opted for early retirement, or so my mechanic told me. The window switch took advantage of the window of opportunity that exists between the time the warranty runs out and the time the last car payment is made. For some reason, auto parts find this a fortuitous time to stop working.

My switch decided to phase out slowly; instead of quitting entirely, it would work part-time. The window could go down as far as it wanted, but the switch would only let it go part way up before stopping the motor.

Ordinarily, a broken switch should be one of life's minor miseries. Fixing it is more of a nuisance than dragging out a stepladder to replace the lightbulb over the stairway, but less frustrating than paying for a plumber to unclog a drain.

This broken switch, however, blossomed into a full-blown $400 pain in the posterior thanks to the wonders of modern technology and the creativity of German engineers.

We're talking Volkswagens here, not BMWs or Mercedes. How the creators of the people's car that lasted longer than thtored on microfilm or computers. Just keeping track of them all costs a fortune, and keeping one of each in the backroom in case it breaks costs even more. Besides which, it is an immutable truth that the one little part you need will always be the one that is out of stock.

So instead of replacing individual parts, we replace entire components and subassemblies. Instead of stocking an electric window motor and 102 other greasy little pieces of metal, plastic and rubber, the parts cage needs just one item -- No. 533-837-401-A.

There are great efficiencies in this. Keeping track of one big part is clearly cheaper and easier than managing an inventory of 102 little ones. When you have 99 percent fewer parts to inventory, you're more likely to have what you need in stock. And installing a power window mechanism that goes in with five bolts and a plug connector is quicker -- and therefore cheaper -- than taking the thing apart to fix it.

Keeping this efficiency in mind is very important when you are shelling out $331.70 for an electric window mechanism and all you need is a new $3 switch.

But it's easy to forget about efficiency after you learn the offending switch and its motor can be removed by a klutz journalist with a Swiss army knife in less than one minute. Presumably it could be replaced in only slightly more time at slightly less cost than $331.70, but that would not be as efficient. At least not as efficient at extracting money from the customer.

It took me a couple of days to learn this lesson in efficiency, during which I avoided total immobility (if not outrage) by turning to my favorite off-the-wall auto rental outfit. For schlepping back and forth to work, I do not need to be transformed into a gold-chained Camaro jockey by National Car Rental or led through an airport full of defensive linemen by O. J. Simpson. I need cheap wheels.

There are none cheaper than the used-car rental outfits that have sprung up recently. Drive-a-Bargain, Rent-a-Wreck and Colonel Clunker's Rent-a-Junker do not promise to try harder. But for $10 a day or less, they will rent you an an almost-over-the-hill Plymouth Duster, a vintage GM gas guzzler or a Chevette with a bad clutch, torn carpet and no gas cap.

I took the latter, turned over my driver's license and credit card and got a sales pitch from the clerk that outdid even my efficiency lesson.

"Our regular rate is $10 a day, 10 cents a mile," she smiled. "Or we have a special at $18 a day with 50 miles free."

She must have seen me coming. I don't think I look enough like Rodney Dangerfield to pay $8 for $5 worth of free mileage, but clearly the clerk had me pegged. Somehow she knew I was the kind of person who would shell out $331.70 for a on/off switch and be stupid enough to tell people about it.