I was recently seduced by a commercial for the just-introduced Dove shampoo and decided I would pick some up the next time I went to the grocery store. At Safeway a few days later, I found the shampoo displayed prominently at the end of an aisle (a display called an "endcap"), but something important was missing: the price.

Though I looked for the shampoo with the intention of purchasing it, I was struck by my sudden ambivalence. I'm sure I would have grabbed it without a second thought if the price had been clearly marked -- whether it had been $4 a bottle (a good buy) or even $8 (it must be good!). But the lack of a price stopped me just long enough to make me ponder how silly it was to be buying new shampoo anyway. After all, nothing in a bottle was ever going to make my hair look like the model's hair in the commercial.

I walked away from the shampoo with a lingering question about how shoppers are affected when a price is not clearly marked. Does it make them more or less likely to buy something? And how much do stores care?

For consumers, "it is a pretty widespread irritation," said Mona Doyle, editor of the Shopper Report, a market research publication based in Philadelphia. So why does it happen so much? At supermarkets and drugstores, the lack of a price usually seems merely sloppy. But at more expensive retailers, I often wonder whether it's intentional.

Doyle says plenty of retailers don't care much about keeping prices clearly marked, though it may be official store policy to have everything labeled. Even some big chains that stake their reputation on price, she said, fall into this category. "A lot of people say Wal-Mart is the worst," Doyle said. "You're supposed to believe that at Wal-Mart it's a good price or it wouldn't be there anyway."

Because shoppers generally do believe that about Wal-Mart, the chain has more leeway to be less than perfect on pricing -- and that's a benefit to the company. It's a huge manpower challenge to keep prices marked on so many thousands of products, so if Wal-Mart can get away with a little bit of sloppiness around the edges, that's good.

Jan Owens, an assistant professor of marketing at the University of Wisconsin at Parkside, has studied the impact of missing prices and says consumers are more likely to overlook a missing price tag if the environment is familiar or the store is known to have prices in a certain range. Wal-Mart would be a good example of that. So would a "dollar store."

At the other end of the spectrum, however, shoppers at more expensive stores are more likely to walk away from something that's not priced or to hold a grudge against the store for being careless. This is especially true now, when there is so much crossover shopping -- rich people shopping at discount stores and lower-income shoppers hunting for bargains at Neiman Marcus.

There are a couple of reasons tonier stores run a greater risk of alienating customers when something is not priced, Owens said. First, at more exclusive stores, the missing price, once revealed, is more likely to be surprisingly high, and shoppers don't like unpleasant surprises. The second reason involves saving face. In certain settings, Owens says, shoppers don't like having to ask how much something costs; it can be uncomfortable or even embarrassing, especially if the price turns out to be something the shopper can't afford and then has to publicly decline. Such an episode can have a lasting effect.

"If you have a nasty surprise, you are much less likely to trust that retailer that anything will be a reasonable price for you," she said.

This happened to me most memorably at Sutton Place Gourmet, the specialty food store. I once picked up a small, unmarked container of dried apricots, figuring they couldn't possibly be very expensive. I was distracted at the register and forgot to see how much the apricots cost, so when I got home I was horrified to see that I'd paid $8.99 for them. Every person I mentioned that to had the same reaction: "No wonder the price wasn't marked."

Sutton Place, of course, says it never intentionally leaves prices off products, but the chain could certainly be more careful. I often see unmarked products in Sutton stores, and since the apricot episode I am much more irritated by such an oversight -- not to mention that I would never buy anything unless it had a price on it. I don't even ask.

Both Owens and Doyle have tried to impress upon retailers how important it is to get prices on merchandise, but both say the problem remains entrenched, perhaps because store owners don't know what they're losing. "I think that you have an issue where operators would not see this the way consumers see it," Doyle said.

In fairness to retailers, keeping up with prices is a daunting task. Anna Fuhrman's two Proper Topper stores in the District are chock full of interesting accessories and lovely jewelry, but keeping prices on everything is a nightmare, she says.

Tags fall off tiny earrings, stickers are brushed off scarves by browsing customers, and prices are sometimes left off entirely by store employees who don't know what the price should be. Fuhrman knows what that means. If the store is crowded, a customer may well give up on trying to find a price. And sometimes the problem is more like the one with my shampoo: If you have to stop and think about it, you may rethink the whole purchase.

"For every person who asks, there are probably 30 people who don't," she said. "It definitely adversely affects sales when things don't have a price on them."

There are, of course, some retailers that believe that hiding prices is useful, especially those that sell products most consumers don't know a lot about, such as jewelry and art. My friend Lynn Loube, a longtime jewelry appraiser and dealer who has worked in numerous jewelry stores, says hiding prices "isn't to deceive, it's a really good way to engage."

Even if it's not deceptive, though, Owens argues -- and I agree -- that it is manipulative. I'm not cheap, and I've certainly overpaid willingly and impulsively for lots of things, but it still makes me slightly uneasy when I have to let a salesperson know that something might be out of my price range.

Lynn says my problem is that I don't buy enough jewelry. Maybe so, but I shop for lots of other stuff, and my reaction is always the same: If the price isn't listed, it's another chore for me to accomplish before I part with my money. Retailers today don't need more hurdles between them and their customers.

If you have a question, comment or concern about what you see when you shop, write to Margaret Webb Pressler at sellingus@washpost.com.