When learning English, full immersion in a English-speaking country is often considered one of the best methods to learn the language. I agree that it is the best way, although it can be also quite expensive when compared to other types of studying.
Leaving in another country can be an expensive experience but that helps a lot the pursue of a perfect fluency. Immigration methods available to study languages abroad are not cheap nor easy. When talking exclusively about courses focused in idioms, most of them are more expensive than, for example, vacationing in the country, since the student would have to spend a longer time in the country and, sometimes, without working. As a result, methods like English courses in non-English-speaking countries can’t be ignored as a valid kind of acquiring proficiency.
However, in terms of the speed and quality of learning English in countries like the UK, USA or Australia, it is faster and better to learn the language there instead of in your homeland with English courses. That owes to the fact that in a foreign place with a different language, you can’t relly on your own mother tongue and will be surrounded completely by the one you will be trying to learn. My work collegue, for example, improved a lot his English skills when spending 6 months in Australia.
In conclusion, despite the price, studying English in an English-speaking country is, in my opinion, the best way to learn it. As a result of being exposed to the language every minute of the day, in a myriad of different situations, the person can learn in a greater velocity and have a better vocabulary and pronunciation.