Clarification on the RS-68 and ET

This From PhysBrain at Spaceflight Sandbox:

Just thought I'd offer a clarification to your comment about why NASA went with the RS-68 (because it could handle the 33' tank). The RS-68 was selected because it would be cheaper to make and throw away after each use than the SSME, but in order to use it (and probably a major reason why it wasn't selected in the first place) is that the current external tank size would not hold enough fuel to power the RS-68's. Once they realized that in the long term, it would actually be cheaper to make the modifications to RS-68 and build wider tank, they found that they also gained a significant increase in overall performance of the CaLV. Less fuel efficient, but more mass can now be thrown to the moon.