You might be more interested in an ethnography of eBay sellers / etc than the algorithmic question. They're typically lower-middle or working class Americans, often severely underemployed (SAHMs are common), who make margins which are actually negative if you impute any cost to their time. They're even more sensitive to losing $3.12 on shipping than PhD students.

This feels to me that this is probably news to you, which is why I'm making it explicit. Given this background, talking about their algorithms sounds silly: they're not sophisticated Internet businesses with Stanford CS majors optimizing for ROi, they're closer to flea market merchants and their accounting controls would have gotten them dismissed for incompetence by any bank in Renaissance Italy.