But still, do the math, they aren't worth it at the current price except as cool novelties. 
Hang on, I've been using 0.07BTC per Eruptor and 330 MH/s as a base for estimating the cost efficiency of most everything else, and so far have only found one unit that's truly for sale that actually beats it.
For example, at the moment Canary also sells blades for 2.75BTC. Those run at about 10.7 GH/s. So we take 10700 and divide by 330, and get ~32.4. So it takes that many eruptors to equal the hashing speed of one blade. Let's round up to 33 units, and multiply 33 by 0.07. That gives us a cost of 2.31BTC worth of eruptors to equal the hashing speed of a 2.75BTC blade. Same speed, for 0.44BTC less.
The eruptors win! Or is my math completely off?