It varies a lot depending on the browser features you're using, total script size, minification vs gzip compression, cache hit rate, etc.

My company is in adtech so our final bundles are 14kb (single TCP congestion window) for modern browsers, 30kb for Safari/iOS 10, and 75kb for IE11/IE10. We've seen similar doubling-of-size in other libraries for backwards compatibility, although we can probably drop IE10 soon and cut IE11 down by half.