A few weeks back, the teen-age son of Ray DeVoe, the 50-year-old investment strategist of the brokerage firm of Bruns, Nordeman, Rea & Co., put the bite on his dad for $5 to take a girl out for pizza. The elder DeVoe rebelled, explaining that in his courting days only a kept woman would cost that much. His son quickly pointed out that five slices of pizza (three for him and two for the girl) at 65 cents each came to $3.25. Throw in another 75 cents to $1 for sodas and that's just under $5, he told his father. Resisting the impulse to tell his son that he could have taken a date to New York's famous Stork Club for $5 in years gone by, DeVoe handed over the money.

That incident with his son made DeVoe wonder about the soaring costs of the dating game. Just how costly is it? And how does it compare to the prices of the mid-50s. He decided to find out. And so, after considerable homework -- which embraced his own dating experiences, plus conversations with both aging bachelors and teen-agers -- DeVoe compiled what he calls "the cost of loving index."

DeVoe very quickly discovered that energy, gold and real estate aren't the only things that have far outpaced the rise in the consumer price index.

He found that his "cost of loving index" has risen almost twice as much from mid-1974 as the advance in the consumer price index -- 340 percent versus 172 percent. And the cost of an average date has climbed even higher -- 352 percent to be precise.

According to DeVoes calculations, just an average date on a national level -- one consisting of a local movie, an inexpensive restaurant with a drink each and dancing (with two more drinks) at a local disco (not Studio 54) -- now runs about $43. And in mid-1954, the same date -- with the local dance hall or nightclub replacing the disco -- averaged around $9.50.

It should be pointed out that DeVoe's index is based on New York experiences. And prices in New York do run higher than in the rest of the country. But DeVoe tells me price increases still would be comparable with other places because they simply would be starting from a lower base.

To appreciate the rocketing costs of the dating game, it's worth going through the various wooing stages.

If you're the romantic type and you'd like to stop off at a piano bar on your first date, get ready to pay through the nose. That soft music (along with a couple of drink) will cost you about $30. That's 400 percent more than $6 tab it would have run in the '50s.

Want to impress your date by going to a nightclub? The check will run $35 (provided you're not a big drinker). Way back when, the same evening ran $10. (

Ah, now the tender trap. A blood test: up to 186 percent from $7 to $20; a marriage license: still a bargain by inflationary standards because it has risen less than the CPI -- only 150 percent from $2 to $5. there's also a week's honeymoon special in Bermuda; it's up 202 percent from $285 to $862.