That's been quite false in my experience - quite a few times it was much easier / simpler / cheaper to build than buy, because there wasn't an offering good eno

That's been quite false in my experience - quite a few times it was much easier / simpler / cheaper to build than buy, because there wasn't an offering good enough, and the cost of adaptation was on the order of the cost of building. Many SAP and Oracle-software (not the DB, the other stuff) implementations fail, and take years to do so, after costing as much as building in house would have (and likely succeeded). For some things, it's true - but I wouldn't consider this "generally applicable wisom"