Hallmark Cards, one of Britain's largest producers of greetings cards, says the market for Valentine cards is £27m, and Interflora, the floral delivery service, forecasts £22m will be spent on flowers in Britain on 14 February alone.
Then there are the candlelit dinners, champagne, chocolates, soft toys and messages of love from Honeybun to Frog in national newspapers - which are harder to quantify.
These public demonstrations of love had humble beginnings. Valentine is generally thought to have been a 3rd-century Christian martyr who miraculously restored the sight of his jailer's blind daughter. Before he was executed he sent her a note from "your Valentine" and the phrase became an enduring symbol of friendship, love and affection.
It was not until Queen Victoria's reign that St Valentine's Day became a commercial entity and the first mass-produced cards were created. Queen Victoria herself sent more than 2,500 cards during her reign.
Cards have remained consistently popular. For those who hanker for something original, Christie's now holds an annual auction of early Valentine cards at prices starting from about £30.
For more run-of-the-mill offerings Kate Duffy, senior buyer at the card retailer Paperchase, says: "So far sales are up 10 per cent on last year. Hand-made cards are doing very well. It seems that people don't flinch at spending £3.95."
Traditional images, such as cherubs and works of art, are particularly popular this year, although there is plenty of demand for so-called humorous cards.
Hallmark's product marketing manager, Dixie Hambidge, says: "There is a resurgence of interest in traditional cards, but buyers are also getting younger. We estimate that children from 10 upwards are now buying Valentine cards."
Although a mere card may suffice for the parsimonious, the more generous lover can fall back on that old standby, chocolates and flowers. But it is only in the past 20 years that companies have started tailoring their products to cash in on St Valentine's Day.
David Mitchell, managing director of the specialist chocolate company Thorntons UK, says: "We have been doing Valentine products for some years but the range has got much wider. We offer heart- shaped plaques which can be iced with a message, as well as milk chocolate arrows and gift- wrapped boxes."
The company also produces the unromantic "Orris the chocolate Orangutan". Mr Mitchell says: "He's a fun thing and we don't censor the messages iced on to him." He adds: "Valentine's Day is our third most important sales period after Christmas and Easter. Sales held up during the recession, probably because these are fairly low-cost items." The company expects to sell more than 25 million chocolates and a million chocolate novelties in the run-up to 14 February.
Interflora has expanded its product range. Last year it introduced "Valentine's Heartbeat", a single red rose, and its own hand-made chocolates. But the biggest seller by far is still the classic bunch of red roses. These are imported from Kenya, Israel and Colombia and because demand is so high they are at a premium. From December to May a dozen red roses from Interflora cost at most £25.50, but during the Valentine period this rises to £35. An Interflora spokeswoman says: "We encourage customers to send other flowers, but the trouble is the rose is considered the most romantic flower."
One business that is taking full advantage of St Valentine's Day is the Vermont Teddy Bear Company, which launched in Britain two weeks ago. It is selling a range of traditional teddy bears dressed as Cupid, a "fool for love" jester, and Mercury, the messenger of the gods. The bears are ordered by telephone and cost from £39.95. Marc Sherman, European marketing director, says: "Valentine's Day is one of the biggest holiday events in the US and that is why we decided to bring the concept here." The company is expecting to establish steady sales of Valentine gifts, but says its products are suitable for all occasions.