There is a catch, Garg. The Pi computers are very minimal devices which can generally only do one or two simple operations, such as being light switches or operating cameras. In general, they are best adapted to being used as teaching devices.
Having sat in seminars about them, I would say their biggest selling point is that they have a large "cool" factor. For example, the radio control panel on a multichannel analog model airplane or drone unit is much more flexible when installed, even if it is more expensive.