One might make a general claim that as any coin stabilizes, the money spent on generating it will always approach the amount of money received.

So for bitcoin, if miners get X on average to mine it, they will spend X-ε in electricity (in bitcoins case), where ε is a tiny profit margin (or perhaps paying back investment).

This will remain true for any other coin and its proof scheme. The amount spent on generating it will asymptotically approach the amount received. The difference is that it might be possible for the byproducts to be useful.