An ever evolving question, that a bit of AEC & Technology Industry history might help answer. Today, very few AEC companies excavate sites, place concrete, or erect steel. If they do those activities, chances are even higher they don't do glazing, set tile or hang doors. Whether you are a Facility Department, Program Manager, Construction Manager, or General Contractor, there's a range of what core business used to be self performed and what is now subcontracted. This even holds true for Subcontractors, who now have subs. There is a similar history & range with Technology providers. Few American companies actually build the products they sell. Like AEC companies, they often manage the effort, the work being executed by specialists, and often times with the use of offshore resources. Without diving to deep, the manufacturing business is a pioneer here as well, for the most part preceding the Technology business. This is becoming more apparent with cloud solutions & related services as well. Why build it yourself IF you can get a better quality deliverable that let's you focus on what you do best.
At the end of the day, most buyers are evaluating cost & quality, unfortunately in many cases, probably in that order. If quality is second, for any number of reasons, most likely something is missing from the lower cost in the first place. 9 times out of 10, I find buyers making buy vs. build decisions based on comparative analysis from various parties that don't know what they don't know. This often results in a painful & expensive path to arriving at where they could have been much quicker, regardless of whether they decided to buy or build. Achieving same or higher quality (SOHQ) with same or lower cost (SOLC) should be the goal, so do proper diligence, and get plenty of opinions and facts before you jump of the cliff with the wrong chute.