Are you sure that the rate from newbie to CPL will cost only 50k ?
Anyway back to the topic, to be honest. I think study at ground school a waste of money. Since most of the study you can study by text book. Especially if you use bob tait books. You would found most of the cyber exams questions is similar or exactly the same from the text book. In general i would say about 30% or more of your cyber exams questions would be the same. The rest of the 40% would be up to you.
However one of the possitive side about ground school is that, they will make you to concentrate more on your studies. E.g. Bob tait ground school, they will help you finish 1 subject in a week. Whether if you study by yourself, you would tends to become slack and lazy.
In the end is really up to you, which method would suit you best.
Good luck with your training and study.
Regards,
Kyandy