Yeah, I think that's the thing that's missing from the narrative in this article - if certain goods on Amazon are really heavily marked up compared to other sit

Yeah, I think that's the thing that's missing from the narrative in this article - if certain goods on Amazon are really heavily marked up compared to other sites, it's better for Amazon's long-term reputation if people don't don't automatically buy from Amazon and maybe get them from other sites because of the reputational damage when those people realize they got screwed, and so Amazon have an incentive not to add a default buy box button under those circumstances. (Usually this seems to happen with in-demand items that are out of stock from Amazon themselves, and the sellers that aren't allowed in the buy box are third party ones. So basically, it mainly screws over canny middlemen who hope to resell things bought at retail elsewhere at a big markup, maybe even literally getting them shipped direct from places like Walmart to the purchaser.)