Sadly not true. As I have pointed out, the pirates could undercut GW even if they sold at cost, so the pirates will always be cheaper and there will still be people willing to buy from them. And my Radiohead example shows people will pirate something even when it is free. Less people might buy from the pirates if GW reduced prices, but there would alwys be some willing to do so.
There is a clear difference. 3D printers are way more expensive than MP3 players were, not to mention the size and convience difference. There is also the customer demand. People are not clamouring in significant numbers for 3d printers in their home, not least beacuse there is little use the average perso has for one at the moment. Until they reduce in cost and size and the technology improves to increase their usefulness, they will not take off in anything like the same way as MP3 players.