The cheapest I've experienced I mentioned above, $10 usd for 50ml of liquid from China. To me, whether it's China or the US, it doesn't matter. They're both foreign countries and they will both have to go through shipping. Plus I find shipping from China far more reasonable than from the US. I guess I just don't see any advantage, if you're buying outside the country, to buying US.
As far as shipping...my last order from China took exactly 7 days from posting to being in my hands, for $15. My order from Happy Vaper, ordered monday, won't be here until next monday. Same time in shipping, and it cost me $13. So not a huge advantage there, as long as customs doesn't hold things up (which is always a risk).