marpoo: I did train in the US and the cost came out to around $19k. This includes getting all three instructor ratings, initial, IR, and multi. However, this was two years ago and the prices have gone up significantly since then. Also, I worked at the FBO so I got a discount on the aircraft and sometimes free instruction.
If you can still get the VISA, and work in the US after getting instructor ratings training in the US is a pretty good deal. However, instructor jobs are a lot harder to find over here right now then they were a year ago.