Just because it costs $50 to produce doesn't mean it'll be sold for that much, lol..
The design is open source and under a public domain and non commercial license. All of the designers in the e-NABLE group (almost 700 people globally) have given away their intellectual property to the World for free.
This means that you can download the files, find one of our volunteers near you with a 3d printer and who can modify the size and shape for you to fit your specific hand and get your device printed or you can invest $400-$3000 into your very own printer and print your files at home - for the rest of your life and any time a part breaks - you just print a new one.
There are people that are selling these - but why would you pay a few thousand dollars to have one printed when you could get yourself your own 3d printer for the same cost and make them yourself?
It takes about 6 hours to print a full hand - and about 2-3 hours to assemble it. If a finger breaks - you print a new one for about $1 in plastic and replace it.