From a technical perspective: prices change constantly; prices are inconsistently expressed and the volume of products is massive. Scrapping the volume of data

From a technical perspective: prices change constantly; prices are inconsistently expressed and the volume of products is massive. Scrapping the volume of data required and then processing it and updating it is a substantially difficult task. From a business point of view an independent operation would require a very large investment. To recoup at least part of that requires advertising and affiliate revenue which in turn creates perverse incentives.