It is my understanding, may be I’m wrong, that the SSMEs being reusable are not something that has an assembly line putting these things out in the 10s or hundreds. As of right now they have need for only 9, 3 for each of the remaining shuttles, plus maybe some spares. Beyond that how many could there be? If they are going to be using them in the new architecture, which is not to be reusable, then they will have to be making them on an assembly line with an output of some number on a continuing basis.

In this form do they need to be made re-usable? It would seem the specifications would be different, and not as strenuous as they would be for re-usable rocket engines. It might be more logical to chose a none re-usable engine already in production. Much simpler, and less expensive to be sure.