In string theory, one of the many vibrational states of the string corresponds to the graviton, a quantum mechanical particle that carries gravitational force. Thus string theory is a theory of quantum gravity.
Their average web application development cost is around $500K and their staff or contractors' salary is in the six figure plus range. Their proposals are usually based on a lot of fluff with the development rate ranging from $400 - $800 per hour. These types of companies focus on custom development.
Apps built by the largest app companies, the big boys, likely cost anywhere between $500,000 to $1,000,000. Apps built by agencies like savvy apps cost anywhere between $150,000 to $450,000. Apps built by smaller shops, possibly with only 2-3 people, likely cost anywhere between $50,000 to $100,000.