Actually, the figure 14.2% does not even appear in the research article. The experiment was between two groups of random Mechanical Turk workers: one group was not shown the cost breakdown while the other group was. The workers answered how likely they were to buy the product on a scale from 1 to 7. If you calculate the average increase from one group to the other, sure enough the number you get is 14.2% but it is not a probability.