What did it all cost? Her lips are sealed.

Like many young professional women, Hilary, a public relations manager in New York, loves fashion. But to keep her boyfriend and her parents from knowing what she spends on her wardrobe, she murmurs three little words to sales clerks: "Is cash OK?" Presto! No monthly credit-card statement, no paper trail.

"I love beautiful clothes and accessories," explains Hilary, who is too embarrassed by her sartorial secret to use her last name.

Despite women's growing economic power and independence, the cost of their wardrobes remains one of the best-kept secrets in many homes. Even wives who earn money and need to dress well for work and social events often don't want their husbands to see the bills. As a result, this "Shh-h-h, don't tell" accounting is surprisingly common at all economic levels, according to fashion retailers and wardrobe consultants.

The secrecy stems in part from women's guilt about spending money on themselves. But it can also reflect deeper issues in a couple's relationship.

"Money is very tricky stuff," says B.J. Gallagher, an author and social psychologist in Los Angeles. "It's interwoven with power, control, and questions such as, Whose money is it? How much is your money? How much is our money? With couples, money is often the arena in which they act out their tugs of war."

Some women, like Hilary, pay cash for nearly everything in their closets. Others charge one item at a store and pay cash for the rest. Still others use a separate credit card that their husbands don't see. Some enlist a friend to buy the items, and then repay her.

Other shoppers cut off the tags when they get home and tuck away purchases. A Boston hairstylist who has a penchant for shoes throws away the boxes before walking in the door.

"They don't want their husband questioning them like [they are] a schoolgirl," says Debbie Mandel of Lawrence, N.Y., who counsels women about relationships and stress management. "They don't want him asking, 'Why did you buy this, and for how much? What were you thinking?' "

A woman who identifies herself only as Leona explains that her boyfriend criticizes her for spending too much on clothes. But, she says, "I don't pass judgment on his golf club purchases."

Part of the challenge stems from a gender gap in the price of men's and women's clothes. For women, being well dressed requires a greater selection. They must also keep up with changing styles.

"A man can get a really great suit for $700 custom-made in New York, or one off the rack for $400," says Waheeda Ali-Salaam, co-owner of OKW, a boutique in Boston. "A guy keeps a suit for 20 years. A woman is going to buy a suit every year."

In addition, a man might own only black shoes, brown shoes, and loafers, all of which he gets resoled. Women need more variety, and their footwear costs more. If women themselves wonder how a few straps stitched to a stiletto heel can set a budget back by several hundred dollars, how can men not be even more puzzled? "Manufacturers really get you for shoes," Ms. Ali-Salaam observes.

Gender differences take other forms as well. "A guy thinks it's crazy for his wife to buy another black skirt," says Ali-Salaam. "She tells him, 'No, dear, this one's a different shape and weight.' "

Because men traditionally earn the money, they feel they deserve to spend it, Ali-Salaam adds. But, she notes, "I've not met any women who don't feel somewhat guilty when they spend more than they perceive they should. It doesn't matter how wealthy they are."

One shop owner who requests anonymity tells of a customer who lives in a multimillion-dollar house and earns a good salary. Even so, when she bought four items during one visit to the store, she went to the bank and withdrew money to pay for them. As the owner explains, "Her husband wouldn't disapprove of it, but he would see it as frivolous."

The same owner also meets couples with the opposite attitude. "I have husbands come in here all the time and say to their wives, 'Get that and that.' The women will say, 'Oh, let me think about it.' They feel guilty spending. He will have just come from Louis [an upscale clothing store in Boston] and spent something, but she can't do it."

Some of that reluctance may be rooted in cultural changes. Prior to the 1960s, when most women were homemakers, a notion of entitlement prevailed, says Samantha von Sperling, director of Polished Social Image Consultants in Boston. "You got married and took care of your husband, the children, the house. Your husband took care of you. The understanding was that he paid the bills and provided for the family. The wife was expected to represent the husband, so he would make an investment in her. His wife was a reflection of him and his ability to provide."

By the 1970s, as legions of women embarked on careers, domestic roles and expectations shifted. Now, Ms. von Sperling says, even though women have more power, their sense of self-worth and entitlement sometimes appears to have diminished. "They'll spend money on themselves, but they'll still feel guilty."

Motherhood can pose another obstacle. "Many women who are home with kids don't think they deserve to spend money on themselves," says Mary Lou Andre, author of "Ready to Wear" and a wardrobe consultant. "They're not working, not bringing money into the house. But taking care of children is tremendously taxing, and you need to feel good about yourself."

Another guilt-producer is the bathroom scale. "A lot of women don't feel good about spending money on clothes when they're not at the perfect weight," Ms. Andre says.

Still, for every anxious underspender, there are plenty of guilt-ridden overspenders. Ms. Mandel sees many "notorious shopaholics" among younger women, who like to have the latest trends and styles.

Hilary knows all about it. She recently placed her name on a waiting list for a Michael Kors rabbit vest, even though the purchase, like others before it, will strain her budget and require yet another cash payment to cover her tracks.

"I'm pretty on top with the other aspects of my life," Hilary says. "I volunteer, I'm successful at my job, I'm politically active. But I must look chic while doing all of that! And honestly, I don't lie about other stuff."

Lying, fibbing, hiding purchases - it's all behavior that Ms. Gallagher, author of "Everything I Know I Learned From Other Women," sees as ultimately self-defeating. She offers the example of women who store a new outfit in the back of the closet, and then pull it out much later. If a husband asks, "Is that new?" they'll say, 'Oh, this old thing?' "

Says Gallagher, "She makes her own money, but she's still not brave enough to say, 'Yes, it is new. Thank you for noticing.' That would be her way of claiming her own power. But by hiding the purchase, or fibbing about it, she's still submitting to him as, 'Well, you're the boss, whatever you say goes, dear.' "

Even so, Gallagher is quick to empathize. This kind of behavior "doesn't make women bad," she says. "It's what we resort to so we feel we have a little more power than we would otherwise."

Whatever the dynamics of a relationship, von Sperling says, "It's important for women to invest in themselves, whether it's a foreign-language class, a cooking class, or a new suit. Anything that enhances you in a positive way is worth it. Then you have more power to go out and invest in other people around you."