Having played on (and heard people play on) a pBone, I'd have to say that even though it's quite impressive to see what they've been able to do with just plastic, it's still quite some way off from being a 'quality' instrument.

And they do not prove at all that the same can be done for any kind of instrument: trumpets and trombones are a lot cheaper to make than things like bassoons - you can find very cheap brass trumpets on ebay for very little money, some of which are surprisingly acceptable; and a rather good trumpet will set you back quite a lot less than a basson only fit for a beginner.