That's why their target for "emerging markets" devices is five whole seconds of JavaScript compilation, which would hardly be considered acceptable on a device five times as expensive, but that device is not five times as fast on a given core, it's probably something more like one and a half or two, maybe two and a half if you include faster main memory and caches.

Added: I once worked on an ecommerce site where I told my team early on that we would probably do worse than we planned if we built and tested on the latest iPhones and Galaxy devices, and was vindicated basically every week after a certain point. It was so bad that, on 802.11ac WiFi connected to a gigabit downlink with about 15ms round trip latency to the servers, the homepage would take about 10 seconds to display anything at all on an iPhone 6s, and another 8 seconds to finish loading the visible content. Unbelievably, more than three quarters of that time was spent parsing and compiling JavaScript. You don't even want to know what happens when you try to open that site on anything slower than a late 2015 flagship device.