One piece of evidence may be to look at the falcon series. I wouldn't say they slowed development of the series so that they could use their older, already established versions. In fact, they designed block 5 to be even better on re-usability, which would increase profit margins by decreasing cost of refurbishment. At the same time, they rendered many of their pending falcon heavy flights unnecessary, as they continually incrementally improved the falcon's payload capacity and thrust. If anything, that may have been a boon economically, because using FH for those same launches would require waiting many additional months to receive that revenue.

So, overall, I'd say SpaceX specifically was pushing towards better margin products pro-actively, rather than dragging their feet on R&D to milk an older cash cow.