Well the US version of the Moto G LTE for example is $220 but it only supports bands 2, 4, 5, and 17.
For global use you need 3, 7, and 20 with 4 being pretty useful for South America. That will pretty much help cover Europe, South America, the Middle East, and most of Asia. Add on a couple other bands to make it even better. It of course does depend on provider but the US LTE bands pretty much restrict the phone to the US and US only. Canada even requires band 7 although I suppose you could scrape by with a US phone.
For comparison a Nexus 5 supports bands 1/2/4/5/17/19/25/26/41 for the US version and 1/3/5/7/8/20 for the global version. What I'm hoping is that a global version of the Moto G shows up on the market. The Moto X is kinda broken down into too many regions to be that useful. The Europe one only has 3 bands and the South America one is missing band 20 which is really needed for Europe.
What I'm really trying to avoid is having a phone for the US, Europe, and Asia/South America.