So it's 2,700 hours for a 4-year degree, versus 960 hours in Lambda School, just using your method of calculation. It's also not counting the internships or summer programs that students in 4-year schools usually partake in. And it does not count extracurriculars during the schoolyear, like hackathons, interview preparation, programming competitions, student group projects, etc. Finally, you're assuming that an entire half of a college degree is geneds, which is really not the case. It's more like 1/4 geneds, 1/2 required major/concentration courses, 1/4 electives which many students opt to take technical courses in. So probably more like 3,200 (minimum) to 5,000 hours in a 4-year college.
Learning difficult material means taking breaks and digesting stuff subconsciously.
Therefore, learning anything difficult takes a certain minimum of calendar time as well as hours in the classroom.
Total Hours of College: 4 years, of which 2 years are "core" coursework and 2 years are general education.
2 Years * 2 semesters per year * 15 weeks per semester * 15 credit hours per week = 900 hours for a degree.
Lambda School: 6 months * 4 weeks per month * 40 hours per week = 960.
Obviously this doesn't account for a number of variables such as 0-credit "mandatory" labs, out-of-class work/projects/studying, but a Lambda student who spends an extra 5-10 hours per week during the program would end up with 1000-1200 total hours.
But this still ignores the main advantage of a program like Lambda, which is the ISA. An education that would be inaccessible to students at the margin -- think people who can't afford to move to a university, qualify for loans, or take 2+ years off of work -- can get in if they're committed enough. Even if Lambda were a total scam, at worst you're out 6 months and $0. If Local State University doesn't get you a job, you're out 4 years and $50k+.