It might (clearly does) look like a rip-off to you at the moment, but you will eventually see the benefits. After attending the compulsory residential part of their distance learning course, the vast majority of students realise that they would never have passed the exams without it.
Most start this phase of the course feeling very unprepared for their exams, but finish it feeling fully ready and eager to get on with them. It all depends on the quality of the training of course, but most schools do a very good job of preparing their students for the exams.
The cost of all of this depends upon which school you choose. Some will charge very high prices, while others will not. The price charged has more to do with the marketing strategy of the school than with the quality of the training. Choose wisely and you will get value for money.
Starting out on this (ATPL) road by purchasing study guides is most certainly the wrong thing to do. Before anyone starts buying anything they should note that in order to qualify to sit the exams they will be required to complete a JAR aproved course of training, which may be full-time or distance learning. The various study guides are intended to help students who are doing this formal training, but these guides can never replace that training.