Piper Jaffray analyst Michael Olson raised his price target for Amazon.com to $1,850 following last night’s Q1 results. The stock in premarket trading is up 7%, or $107.04, to $1625.00. Amazon reported revenue 2% above and operating income 91% above the Street, while the high end of Q2 guidance calls for 200 basis points of operating margin expansion, Olson tells investors in a post-earnings research note. North America organic retail revenue strength continues, driven by Prime and associated retail volume, while Web Services accelerated, the analyst adds. He believes the increase in U.S. Prime subscription cost from $99 to $119, effective on June 16, will drive $1.2B of incremental revenue. Olson reiterates an Overweight rating on Amazon shares.