Chris Dixon has a great post about this phenomenon:
http://cdixon.org/2012/07/08/how-bundling-benefits-sellers-a...
http://cdixon.org/2012/07/08/how-bundling-benefits-sellers-a...
http://www.slate.com/blogs/moneybox/2013/07/17/a_la_carte_es...
http://marginalrevolution.com/marginalrevolution/2013/05/bun...