Price-quality irradiation is the term used in marketing for the effect whereby buyers infer quality from price. Expensive products are judged to be of higher quality than objectively equivalent but cheaper offerings. If something is free of charge, it is indeed accepted, but it is not otherwise valued: what costs nothing is quickly regarded as worth nothing.
A well-known example is provided by a Swiss watch manufacturer which some years ago offered an inexpensive steel watch for the first time. The price was unusually low for this brand, and the management firmly reckoned on a success; in fact the model proved to be a slow seller. Only after the price had been raised by several thousand DM did the watch sell splendidly, because customers expressly wanted an expensive watch. Something comparable is seen with management consultancies and market research institutes, whose information, known for years, is only actually used once high fees have been paid for it beforehand.