Here’s the conclusion:
I encourage you to consider ‘build vs. buy’ primarily from the lens of whether the opportunity merits a long-term strategic investment of your team’s attention, and less from the lens of short-term financial cost. Build if there’s an opportunity to make a significant improvement on the state of the art and create a competitive advantage for your organization. Buy it otherwise. And be ready to discard your competitive advantages of yesteryear as better alternatives emerge.
Together with Choosing software vendors well, it feels like a coherent a strategy.