$30k in 4 months is practically a 6 figure income already, and not uncommon for CS sophomores working at larger tech companies. I think you're really overestimating the skill needed to get that level of pay.
I think if you rule out CS majors at top 20 (ish) schools/progams, I think that you will find the number of CS major sophomores getting these types of summer internships rounds to zero, and the exceptions exist largely due to pre-existing personal contacts.
I would suggest that most CS majors at top 20 schools/programs grossly underestimate how hard it is to do what they have done.
I know plenty of Cal State CS majors who only dream of jobs like this. These relatively lucrative jobs aren’t really that common for mediocre students at mediocre programs.
