The study they cite seems to be leaving out something: are the participantsforced to make a choice, or could they choose to not take either? If I were presented with the two choices they give, I'd probably take the free one in the first choice but not take either in the second because I just wouldn't care enough to buy the single small piece of chocolate for either price. If I were forced to make a choice, I might pick the Lindt, but I'd argue that then their experiment isn't actually testing the same thing. A forced choice been two things isn't the same as two options that can both be rejected.

there was a no-choice option, it’s in the study (see the graphs)