as mentioned by Guenneal, universities like Harvard and Stanford do normally offer undergrad degrees in Business and Economics. In terms of the MBA, usually people do such a degree for three reasons:
- Business knowledge (in a broad sense - including soft skills)
- The opportunity to change career and become interesting as a hire for companies that otherwise would have not found you interesting
- Develop a network of Alumni from the program
In general, an MBA will position you in a completely different way compared to an undergraduate degree in the job market, in monetary terms. It will also provide a different network of people more keen to a high-level corporate career.
The final decision on what makes more sense depends on your goals. On the one hand, if you are interested purely in knowledge, you may focus on undergrad courses, on campus or even online - there are several top universities offering online classes, which could provide a good way to get qualified relevant information at your convenience. On the other hand, if you are targeting a corporate/consulting path or want to change career, and want to be part of a qualified network, a top MBA would make much more sense.