It is stated that Peter has $50 on hand so it means that Peter already decided that he will spend all or less than $50 for a set of towel. So when Peter saw the two brands of the towel and after inspecting the price and quality, he settled for the higher valued towel. There are many reasons you can see why Peter choose the one which has the higher price at $45 that the cheaper one which is $30. One reason is the quality, but I can see that the main reason is that Peter already decided to spend $50 for a towel before going to the store so whatever towel he sees, he will most likely to choose which is nearer the price he set for buying a towel.