I'll sometimes filter based on "most popular" and the result will be that the top item is som expensive thing that makes me wonder if it's really the most popular. It seems obvious that this might just be a way for the store to manipulate buyers. Does anyone have insight into how these work and is there any real function behind them?
I have worked with a handful of online stores, all of them used different criteria for what was the most popular item. Some were pretty simple like "highest volume of sales in the past 7 or 30 days", some others were pretty complex and some were pretty much dishonest, putting expensive products next to slightly higher than average ones in order to make them feel cheaper. Like the other comment have said, there is no consensus and it mainly depends on the company's goals with that section.