Originally Posted by
ORAC
The Raptor a smaller less powerful little engine compared to the RS-25?
I apologise. I was egregiously confusing the Merlin engines which current SpaceX rockets use with the Raptor which is being used on the Starship. I think It's probable that Raptor wasn't complete or flown when choices about the SLS were being made. I think you still cannot compare them on price yet because one is a leftover freebie and we don't know the price of the newer version of it.