SEATTLE — Amazon is so serious about its next big thing that it hired three women to do nothing but try on size 8 shoes for its Web reviews. Full time.


The online retailer is shooting 3,000 fashion images a day in a photo studio using patent-pending technology.


And it is happily losing hundreds of millions of dollars a year on free shipping — and even free returns on apparel — to keep its shoppers coming back.


Having decimated the publishing industry, slashed pricing in electronics and made the toy industry quiver, Amazon is taking on the high-end clothing business in its typical way: go big and spare no expense.


“It’s Day 1 in the category,” Jeff Bezos, Amazon’s chief executive, said in a recent interview. Though characteristically tight-lipped on bottom-line details, Mr. Bezos said the company was making a “significant” investment in fashion as it tried to convince designer brands that it wanted to work with them, not against them.


The traditional retail world — and many major brands that want no part of Amazon — are gearing up to fight for their lives.


“It has the latitude to set prices and charge whatever it wants,” Sucharita Mulpuru, an analyst for Forrester Research, said of Amazon. “That is a huge threat for brands.”


Amazon has sold clothing for years. But in the last year, it says, it has signed on hundreds of contemporary and high-end brands, including Michael Kors, Vivienne Westwood, Catherine Malandrino, Jack Spade and Tracy Reese, and it continues to prowl for more. On Monday, some of Amazon’s muscle will be on display as the company sponsors, and live-streams, the Costume Institute Benefit at the Metropolitan Museum of Art and the accompanying exhibit. Mr. Bezos, the event’s honorary chairman, said that, on the advice of Anna Wintour, Vogue’s editor, he will wear a pink pocket square with either a Tom Ford or Prada tuxedo (neither of which is available on Amazon).


Amazon’s decision to go after high fashion is about plain economics. Because Amazon’s costs are about the same whether it is shipping a $10 book or a $1,000 skirt, “gross profit dollars per unit will be much higher on a fashion item,” Mr. Bezos said, and it already makes money on fashion. While its MyHabit site, started last year, uses a flash-sale model to compete with Gilt Groupe, Mr. Bezos says the company’s new effort is not about selling clothes at deep discounts but at prices that ensure “the designer brands are happy.”


Amazon has not just size on its side but money. The company has about $5.7 billion in cash and marketable securities, and Mr. Bezos has long taken a stance that investment, rather than profits, is the best place to put it. The company can afford to do things that some competitors cannot. Need to hire a bevy of stylists for the Web site models (which Amazon is doing)? No problem. Want to replace the plain brown shipping box with a fancier package for apparel (which Amazon is testing)? Sure.


Until now, fashion has been one of the few categories that Amazon has tried to dominate without success. In addition to its own site, Amazon bought the shoe site Zappos.com for more than $1 billion in 2009, started the shoe site Endless.com and MyHabit, and bought the boutique Shopbop in 2006.


But many brands stayed away because they said Amazon’s site often looked too commoditized. “It’s not a place where you look at it and are like, ‘Oh, my clothes look and feel really good,’ ” said Andy Page, founder of men’s fashion brand Bonobos, which does not sell through Amazon.


Amazon hopes to fix that problem by going luxe. Mr. Bezos said apparel sales on Amazon.com increased by triple digits in the last year as the new high-end push was introduced, thanks to what he described as companywide support.


Amazon’s considerable computing capability, for example, has been turned to fashion and the analysis of enormous amounts of shopping data. The company has also made a “disproportionate” investment in photography, said Cathy Beaudoin, the president of fashion for Amazon. The photography studio, in Kentucky, can shoot more than two images a minute, allowing the company to post new items daily on the Web that were photographed hours earlier.


“Speed is everything in fashion, and getting it to customers first is the race,” Ms. Beaudoin said.


Most of all, the company is working to improve its presentation, so far most evidently on MyHabit, which Mr. Bezos said represented where Amazon wanted to go with all of its Web design for fashion.


Instead of static product images, for example, models spin and pose to show off the clothing. The model’s body measurements and the clothing measurements are provided to help with sizing. And shopper-friendly advice — does the size 8 shoe run big or small? — has been placed front and center.


The ramp-up has created buzz as the company has hired models, stylists and makeup artists, started using customer data to personalize brand and size search results, and as it runs the first advertisement campaign ever, in print and outdoors, for the Amazon clothing store.


It has also unsettled much of the retail clothing world as fears grow that few will be able to compete with a stepped-up Amazon.


For some brands, the company’s size alone — it is the world’s biggest e-commerce site — makes an overture from Amazon difficult to reject. “The amount of eyeballs and traffic and retail dollars that are generated through their Web site” is impressive, said Alex Bhathal, co-president of Raj Manufacturing, which makes licensed swimwear brands like Ella Moss and has been expanding what it sells through Amazon.


Amazon can also offer brands more attractive terms than many other stores. For instance, while department stores often ask for “markdown money” when items do not sell, or return unsold product to a brand, Amazon does not, said Ron Friedman, an accountant at Marcum L.L.P. who advises brands like James Perse and American Rag.


And to woo brands, Amazon is willing to make big buys. Jason Cauchi, the creative director of Dallin Chase, had been selling some merchandise to Amazon’s Shopbop. Recently Amazon said it would buy items from the entire collection for the Amazon.com site, which Mr. Cauchi said was a rare offer and difficult to refuse.


On the biggest area of concern for competitors — pricing — Mr. Bezos said that, despite having taken a low-price approach in other industries, Amazon would not in fashion. “There’s a sophisticated markdown cadence in the fashion industry that we think makes sense and we’re basically following that established approach,” he said.


There are many disbelievers, given Amazon’s history in other industries. Mr. Bezos, moreover, has to deal with the fact that he is moving into an alien world; he is no fashion guy. Asked in the interview about the brands he was wearing, Mr. Bezos could not name the brands of his shirt or shoes. The jeans, he said, were Prada (not available on Amazon); his blue “Jeff” security badge was dangling from them.