OP/Besalel:
1. You must completely separate the discussion of education pertaining to Limudei Kodesh from secular studies. Some/many parents, may desire — fully within their rights — to forgoe any secular education and focus entirely on Limudei Kodesh and on being a Ben Torah, Yid and mentsch with stellar middos.
This is not only their natural right, but it is a highly commendable choice. Even if you disagree with the parents.
2. To answer your OP, Torah education has not declined with time over the last 75 years. Au contraire. It has markedly improved.
3. Those spending 50% of their income on their children’s education are clearly and absolutely focusing on their second education. To the detriment of their Torah education, I might add, as the secular is then occupying a significant amount of the child’s limited time per day.
No one needs to spend remotely nearly 50% of their income of their children’s Torah education.
4. Not every of what you call “kosher fields” is as kosher as you may think. Some are less kosher than others, even if not outright forbidden. There is very good reason to educate one’s children to the exclusion of gaining a taste or ability to choose a less kosher line of work environment over a more kosher/Jewish field.