NASA in-house projects were historically expensive because they took the approach that they were building single-digit numbers of everything -- very nearly every vehicle was bespoke, essentially -- and because failure was a death sentence politically, they couldn't blow things up and iterate quickly. Everything had to be studied and reviewed and re-reviewed and then non-destructively tested and retested and integration tested and dry rehearsed and wet rehearsed and debriefed and revised and retested and etc. ad infinitum. That's arguably what you want in something like a billion dollar space telescope that you only need one of and has to work right the first time, but the lesson of SpaceX is that as long as you aren't afraid of failure you can start cheap and cheerful, make mistakes, and learn more from those mistakes than you would from packing a dozen layers of bureaucracy into a QC program and have them all spitball hypothetical failure modes for months.

Boeing, ULA and the rest of the old space crew are so used to doing things the old way that they struggle culturally to make the adaptations needed to compete with SpaceX on price, and then in Boeing's case the MBAs also decided that if they stopped doing all that pesky engineering analysis and QA/QC work they could spend all that labor cost on stock buybacks instead.