Re: "The market is forecast to rise from $4.1bn in 2015 to $16.2bn by 2020"
HP has claimed they are going to be able to revolutionize the market by bringing the quality and speed of the $50,000 3D printers to a consumer / small business price point, similar to what happened with laser printers over time.
With such a small number of units sold, it isn't that hard to quadruple the market revenue in four years regardless of whether you are selling at $500 or $120,000.