"We're adding a lot of resources," chief financial officer Tom Szkutak said during a conference call.
Conversely, net sales rose 34 percent to $13.2 billion.
North America segment sales, representing the company's U.S. and Canadian sites, increased 36 percent to $7.4 billion, while operating income rose 20.3 percent to $349 million.
Sales of electronics and other general merchandise in North America rose 44.5 percent to nearly $4.8 billion, or 65 percent of the merchandise mix. Media sales rose 15.8 percent to $2.2 billion, representing 30 percent of the merchandise mix.
The company said the Kindle Fire remains its best-selling product and that nine out of 10 of its top first-quarter sellers were digital products, including Kindle, Kindle books, movies, music and apps.