Indians cannot apply for E-2 investor visas to United States. This is because India does not have direct E-2 treaty with the United States. The only way for Indians to apply for E-2 visa is to become a citizen of another foreign country, which has direct E-2 agreement with US.
Since India does not allow dual citizenship, only possibility is abandon indian citizenship and get OCI status along with foreign citizenship. There are number of countries that have E-2 agreement with US where you become a citizen by naturalizing.
Another very attractive route is to use citizenship by investment schemes running in Grenada, Turkey, Montenegro etc. These countries have E-2 treaty with US will give you a immediate passport if you buy a property or donate to a government fund. Once you become a citizen, you can apply for E-2 visa at any US embassy where you live.
Grenada is the cheapest route which comes as a package with citizenship and E-2 visa (done with US lawyer). You should be looking at half the costs compared to EB-5. To get Grenada citizenship you pay approx $175,000 (all inclusive) plus $100,000 for E-2 visa approval assuming you are one person. You have to remember that Grenada citizenship investment is non-refundable investment. The key criteria for E-2 approval is US job creation.
E-2 investor visas have been popular among Indians, which has been cheapest alternative to EB5 green card program with very fast processing times than waiting for years. Another huge benefit is E-2 visa is non immigrant visa status, only requires about $100,000 business investment compared to $500,000 for EB-5.