I thought that was part of classical homo economicus. If buying something would cause you some emotional disquiet (because you suspect you're wasting resources)

I thought that was part of classical homo economicus. If buying something would cause you some emotional disquiet (because you suspect you're wasting resources), then your willingness to pay for that product is lower, and you won't buy it. So it explains it pretty well. Also, the article mentioned this possibility (that 20 is simply too many) repeatedly.