This is a term that business people -- suits, the Great Santa -- use to refer to the whole process of selling something to a customer.
In Woolworth's, it's very simple and quick, as long as the cashier keeps the line moving along. In fact, it's so simple and quick that you really don't think about it as a thing in itself. With other transactions, it's more complex, and the complexity naturally rises with the cost of the item.
Take cars. Most of us have bought a car, and that's a lot more hassle than buying a tube of toothpaste. There's a real sales cycle there: From the sales rep's point of view, you walk into the dealership and he puts on his big friendly smile. From there (ideally, from where he sits) you might move on to deciding what you want, whether you'll buy it from him, what color, options, and financing you want (or have to settle for), and a host of other major and minor annoyances. At long last, after a few weeks, he may see a check. Then again, you could break off the engagement at any moment before the papers are signed. It's like a mating dance between blind beasts who don't really like each other. The smaller one keeps thinking "hey, wait a minute, what am I doing here?" as the noose tightens, but the larger paws the soil and sings sweet howlings and gibberings in the little critter's waxy, wrinkled ear. As often as not, the little one decides to stay. It's not a very bright critter.
Poetry aside, it's got to be nerve-wracking for the sales rep. That's his dinner on the hoof there, asking stupid questions, dithering, and wondering if its mother-in-law will make fun of the color. Imagine if your dinner had not only a mind of its own, but a disordered one at that.
It gets worse with bigger purchases. A lot of very expensive things are only bought by businesses, who often learn to make decisions by observing gregarious ungulates and Bobby Rahall and then flipping a coin. I once worked for a company that sold software to people who built housing developments. It was six-figure stuff, and those are very stable, careful, conservative companies. The sales cycle never came in much under nine months, and I recall one that took a year and a half. That means that one day they took well to a cold call, or they saw our booth at a trade show or saw our ad in a trade magazine, and they thought they might be interested. The next step was to fly a sales rep out to visit them, sometimes across the country. The reps could only rarely combine visits, because there just weren't very many. Therefore: That's a plane ticket to a city across the country (usually bought too late to get a good price), plus two or three days of hotel and car rental. I never went near the bookkeeping, but that's got to be a couple thousand bucks. For a visit, just to say high and give a presentation. Sometimes that was the end of it. Sometimes there was a second visit, followed by an elaborate formal courtship while the potential customer had meetings and mulled things over. Once they decided they liked it (if they liked it), they had to talk about what they'd pay for it. Nothing that costs $300,000 has a price tag on it. It costs whatever you can talk them into paying for it, and they pay it in whatever small, widely-spaced installments they can badger you into putting up with. Then they've got to decide how to pay for it, and then they've got to get cold feet at the last minute and stop returning your calls for a month. Finally, the sales rep may get a commission, a very long time after that first contact with that customer. They might go out of business before that happens. So might you.
The commission on $300,000 must be a nice chunk of change, but how long has it been since the last one? You've probably eaten every bite of the last one by the time the next check clears, or at least that's how it went for our sales staff. If you just sell more, that'd be nice1, but that's not always easy: Lots of people eat hamburgers, and there's always another hungry mouth walking down the street, but very few people are in the market for gargantuan and fundamentally worthless database systems.
Oh, and do you know how long it takes to sell somebody a jumbo jet or an aircraft carrier? It's not quick.
1 That's the theory. In our case, it would have doubled (at least) the support overhead on a labyrinthine and buggy system, and driven us into bankruptcy even sooner. So it goes.