There are many CA's who do not want to leave India, and work elsewhere.. Family also might be a reason not to go overseas. Many married CA's find it difficult to relocate as well!
Moreover, this high salary was offered by Olam International, it is undoubtedly a good company , Still people consider companies like ITC, TATA, Reliance, etc haviing a far better prospect in terms of growth.
The economic melt down has left dark patches everywhere on the globe, and India still continues to grow! Infact people working outside india for many years are returning, owing to the prediction that India and China would be the most desirable destinations of Investment in near future, which has already started.