There is no logical reason to assume that high prices mean high quality or that low prices mean low quality. In many cases there is no direct link between the two.
More importantly, if you assume that you must pay high prices to get high quality you will miss some very good deals. As an example of what I mean, there is a scheme whereby FTOs can get what is effectively a government grant for each student they teach. This enables the price of a full time groundschool ATPL course to be reduced by up something like £1600. The school's profit margin is not changed so there is no reason for them to reduce their costs or the quality of the course provided.
At the end of the day prospective students must look very carefully at the offers of the various schools. They must then make a balanced judgement of which school best suits their needs.