Starbucks isn’t the place to go for cheap coffee. It is selling an experience, not a commodity.

That approach has been immensely successful, drawing in millions of customers and propelling Starbucks stock to stellar returns. But the company’s strategy has created an odd situation this summer: It has raised retail prices for much of the coffee brewed in its stores just as coffee prices on world commodities markets have fallen.

Once, long ago, coffeehouses were the trading centers of world financial markets. If you wanted to know the price of any commodity, you could find it while sipping coffee in London. But this year, if your only information about commodity prices came from coffee sold at Starbucks, you might have to conclude it was a bull market.

The opposite is true. Coffee has been caught in a commodities downdraft that intensified briefly last week as China, a big commodities consumer, devalued its currency. The currencies of commodity producers like Malaysia, Indonesia, Russia, Colombia and Brazil have fallen for months now, along with oil, iron and steel. Coffee has taken one of the deepest dives.

Yet on July 6, Starbucks said its costs were rising and that it was raising the price of much of its brewed coffee by 5 to 20 cents a cup.

In a statement, Lisa Passe, a spokeswoman, said Starbucks tried to “balance the need to run our business profitably while continuing to provide value to our loyal customers and to attract new customers.”

The price changes in the global coffee market have been breathtaking. The futures price for standard Arabica, the benchmark for premium coffee, peaked in October and fell 44 percent in world markets by July 6, the day of the Starbucks announcement. Some companies responded by lowering prices. J.M. Smucker announced in late June that it was cutting supermarket prices of its Folgers and Dunkin’ Donuts brands by an average 6 percent.

Starbucks’ ability to raise prices has delighted the stock market. Starbucks shares have returned 5.4 percent since July 6, compared with a 1.3 percent return for the Standard & Poor’s 500-stock index. The company has outperformed over longer periods, too. Its shares returned 51 percent, including dividends, over the last year, compared with 9 percent for the index; over five years the return was 412 percent for Starbucks versus 115 percent for the index.