-100ms of additional page load time cost 1% revenue (Amazon)
-400ms means -9% vistors (Yahoo)
-Showing 30 search results instead of 10 and therefore accepting 500ms of additional page load time means traffic goes back by 20% (Google)
-Every second of page load time reduces conversions by 7%
There are many more. There is a nice infographic summarizing a few more studies in a nice way [2].
In fact, I think the trend is quite the opposite: as devices and connections get better, people start to expect that websites are very responsive and load fast.
[1] http://www.baqend.com/product.html
[2] http://infographicjournal.com/wp-content/uploads/2016/02/How...