BARCELONA, Spain — When Ellie Turner decided she wanted an upgrade from her iPhone 3G, she expected to pay more for Apple’s new iPhone 4S than for the other leading smartphones on the market.

Instead, Ms. Turner, a public relations specialist in London, got the fast-selling device free.

She consulted Phones4u, a bulk discounter of cellphones and data packages, which offered her a free iPhone 4S and data plan for £2, or $3.20, more than she had been paying each month. She returned to her operator, O2 U.K., which had been selling the 4S for £99 with the same plan. She told people there about the rival offer.

“They didn’t blink an eye,” Ms. Turner said. “They matched it.”

Apple, the global market leader in smartphones, is enjoying record profits and sales that have transformed it into the world’s most valuable company on any stock market. But the mobile computing industry it has conquered in just five years is changing rapidly, and not even Apple’s trend-setting image appears guaranteed.

Unlike in the United States where competitors find it difficult to price a comparable phone lower than an iPhone, in Britain, the iPhone 4S costs at least £170 more than the Samsung Galaxy S II with a two-year commitment at O2 U.K. At T-Mobile in Germany, the Samsung model costs about 80 euros, or $108, and the 4S 130 euros. But the iPhone retains its enviable image as the phone to which all others are compared.