Rajesh,
as Raj mentioned price erosion should be expected as more and more players get approval. Plus market share also will get reduced over a time.
The main thing here is to see how much the company makes in the limited competition period. And thats where players like torrent have got lucky and were in the right place at the right time. Alembic also benefitted but since it doesnt have its own front end marketing network in US, (which torrent has), it will have to share profits with marketing partner.