Personal computer prices are going down again.

With the Christmas sales season still weeks away, there are unmistakable signs that computer makers are giving in to their basic capitalistic impulses and cutting prices to lure customers.

This is not the way the barons of the personal computer industry had planned things for the end of 1985. According to their strategy, the last quarter was supposed to make amends for what has been a decidedly lackluster year in the PC business.

Worldwide micro-computer sales should increase 23 percent in 1985 from the previous year, according to the market-research firm Infocorp. There are lots of companies in lots of industries, of course, that would swoon with delight over a 23 percent sales increase. But for the booming personal computer business, this is not up to par. That's why you've seen so many news reports about the "troubled" computer industry.

The fourth quarter -- the Christmas sales quarter -- always has been the richest for computer makers and retailers. The industry has been hoping for a particularly strong fourth quarter this year to fatten the bottom line before the books are closed on 1985. To preserve year-end profits, industry leaders have said repeatedly that they won't repeat the last-quarter price-cutting extravaganza we saw last year.

That's what they've said, all right: No price cuts. But watching personal computer makers trying to resist price cuts brings to mind Lord Byron's wonderful picture of the voluptuous Donna Julia trying to resist Don Juan:

"A little she strove, and much repented,

And whispering 'I will ne're consent' -- consented."

It looks now as if the PC people will give in to the old temptation again this year:

* Item: Apple has just announced retail price cuts ranging from 11 percent to 24 percent on its IIc, IIe, and 512K Macintosh computers. The suggested retail price for a standard IIc with an amber monitor, for example, has dropped from $1,295 to $995; many retailers are discounting the package further, down to $850 or less.

* Item: IBM, striving to unload more than 150,000 PCjrs still cluttering the warehouses, has begun a major promotion for dealers that should lead to a retail price for the PCjr, with color monitor, of $595 or so. That's about $200 less than the little computer cost last Christmas; it's $1,400 below the suggested retail price two years ago.

* Item: Among IBM-PC clones, a standard business configuration -- a computer with 256K of memory, monochrome monitor, two floppy disk drives -- can be had almost anywhere for around $1,500. Several clone makers, including Corona, Leading Edge, Tandy, and Zenith, all have announced prices lower than that for the Christmas season. Last year, the same configuration averaged $1,800 or more.

On top of all that, this fall marks the return to the personal computer market of the greatest price-slasher of all, Jack Tramiel. When he was running Commodore, Tramiel was famous for cutting prices every time he saw the slightest dimple in the sales curve. Now Tramiel owns Atari, and he's got a brand-new product to sell: the spiffy new $1,000 Atari ST. Atari says it will hold firm on the ST's price. If you believe that, I've got the Tooth Fairy waiting for you in the next room.

Most of the Japanese micro-computer makers are cutting prices, too. But loyal readers of this column know that this fact is irrelevant. Americans should buy American-made computers -- partly because they're better and partly because they're American.

The one exception to the price-cutting craze -- remember, you read it here first -- will be none other than Commodore. It looks very much as if Commodore has a real winner in its new machine, the Amiga. This fast, powerful new computer already has made the cover of Byte Magazine -- the computer industry's equivalent of the Congressional Medal of Honor -- and retailers have waiting lists of eager buyers.

Under those circumstances, you can expect Amiga's price -- $1,295 for a 256K, single-disk-drive system with some bundled software but no monitor -- to hold steady for months to come.

For almost any computer but the Amiga, though, prices are heading downward, and just in time for Christmas. Fa la la la la, la la la la!