What are the benefits of studying in uni longer compared to get a degree and make that money?

Depends what you want to do with your degree. If you want certain types of jobs, like an academic in that field, a PhD is a must. If you want to go into a slightly different field or a lower level, it would probably be best to just go straight out to work after the degree, and if you need further study later on you can go back to it (some employers give you time off, or money, to do a Masters for example). There are some areas/jobs where you can make a large amount with just a Bachelor degree, but others where to advance to a high pay rate you'd need further qualifications.

Harriet