So recently someone found out that the industry studies for SLS had been FOIAed by a site called government attic. While the other studies are interesting in their own right (check them out honestly), the United Space Alliance study (includes SX study as well) has a detailed analysis on various RAC concepts. It has a expansive list of engines for the first and second stage of SLS and while the information on engine unit and dev cost has been redacted for propriety reasons in the first stage engine table, there was a paragraph before that which states:
The RS-68B first flight engines would be available approximately at the same time as the RS-25E due to existing work already accomplished under the advanced Ares V engine development. A small amount of engine development cost on integrating the RS-68A would be required, and the recurring cost per engine set (five RS-25E versus four RS-68B) would be significantly more (approximately 90 percent per engine; approximately $165M per flight set) for the SSME derivative.
This paragraph should provide a cost estimate for the RS-25E, however I have no clue on how to interpret it. (Originally I thought this was the source for the 40 mil a pop because 165/4 = ~40, but this is obviously wrong because there at 5 RS-25E for this stage)
So how should this sentence be interpreted?