it can be quite a lot. you can test using a CDN or a setup like this and the too...

mxpxrocks10 on July 28, 2014 | parent | context | favorite | on: Rolling your own CDN for $25 in 1 hour

it can be quite a lot. you can test using a CDN or a setup like this and the tools over at www.webpagetest.org (from Patrick Meehan - who is awesome) from different locations.