Old discussion here on HN, but the claim is made that every 100ms latency cost 1% in profit: https://news.ycombinator.com/item?id=273900

HTTPS is pretty fast now with SPDY (and soon HTTP/2) but there is no avoiding the fact that is slows down that first page load ever so slightly. No doubt they have studied this carefully and opted for maximum speed, as this maximizes income.