not that many CS jobs needs highly trained graduates

Companies need to make money, if a person paid 250k is doing the same job as one payed 140K, they will fire 250K ones and keep 140K. There are people who started those kind of lies.

Companies may pay 10% higher at starting jobs for elite school graduates. After that, the salary is tied to values they create for the companies, doen't matter where you graduate from.