Effectively the government paying you to move there by allowing you to not pay any taxes. So if your company is paying $2m/yr in taxes, you're being paid $2m+ to move your operations. You'll lose some of that to construction costs, but you'll likely more than make that up by paying (comparatively to previous employees) slave wages to locals.

It's a thing to encourage foreign investors.
Honestly, if the Modi govt. is still furthering that strategy, I think that they are out of good ideas and should hand over to another.