(if dear reader, like me, had no idea what ECM meant in this context).
On the other hand, at least it's _possible_ to make your own at home: http://makezine.com/2008/01/07/make-your-own-vacuum-tube/
I somehow doubt there's many talented amateurs assembling MOSFETs in their garages...
(if dear reader, like me, had no idea what ECM meant in this context).