It's almost a natural law of economy: when a commodity becomes very widely available the price will fall. As demand rises the availability of things will increase because the manufacturers and sellers are interested in serving the market and raise the production. As a result the number of goods available to that market will increase and in order to get a cut, some sellers will lower their prices. Customers generally prefer buy at low prices and if you want to sell, you have to follow the price reductions.
When such a commodity at the same time is becoming more and more easy to produce and is produced by an exploding number of people, you have a price-reduction spiral that goes almost all the way down to free.
