I'm not sure that online shops are any less likely to try "to manipulate for maximum benefit". The palette may change (fresh bread smells & video surveillance get replaced by cookies and Referer fields) but the motivations and biases stay the same.
Of course, but my point is that the online shops have a much narrower range to work in. If a grocery store makes you walk around a quarter of a mile to get a ten-item list of necessities, people will accept it. If an online store makes you view half its inventory before you can purchase something, it's not going to make much business.