Most people who join MBB fresh out of under grad do it for the career prospects. Money starts to get more interesting most MBA. After 2 years as analyst and 2 years of MBA, you come back to 12-13k monthly as associate (in Mck). As an EM (which is 2 years after Associate), you get ~250-300k annual. AP gets 300-500k and as a Partner (which is 8-10 years after graduating including MBA time) you are looking at 700k-1.2m annual comp. Which is pretty decent even if these people can probably get more working in finance or tech.