The problem with "energy too cheap to meter" is that it has to very quickly become "energy too cheap to make a profit from". And that is the _real_ obstacle to prolific nuclear.
That wasn't the original hope -- formerly, they hoped nuclear plants would be cheap and plentiful. My understanding is that "too cheap to meter" just refers to a flat rate -- why bother measuring (especially before modern times, back when that required people visiting meters in person), when you can charge a flat rate? But that clearly was extremely optimistic.