Hi Grace. I understand your concerns. However I would not "over stress" about what undergrad school you go to. It is much more important to get excellent grades (and do well on the MCAT) at whatever school you enter, as opposed to the name of the school itself, although of course I can't deny that name recognition has some effect.
Your worry about cost is very understandable. Both undergrad and medical schools can vary greatly in terms of cost. You should pay attention to the academic quality of both, but there are definitely "good" schools that cost much less than other comparable schools. Some details:
1) I went to Baylor College of Medicine in Texas; my brother went to Yale Med. He ended up owing a lot more money in loans, but there was no significant difference in our test scores (USMLE) or eventual residency placements. We both did pretty well.
2) When you actually become a doctor, you will realize that no one cares where you went to medical school (although they might be interested in your residency or fellowship). That being said, yes - residency programs will care where you went to medical school to varying degrees. But in my neurology class at UCLA, we had a broad mix, and some of the most excellent residents were from less "famous" schools. Again it is most important to just excel wherever you are.
3) Finally, keep in mind your eventual earning potential as a doctor...including what kind of doctor you wish to be. (Average salaries by region and type can be looked up on the internet). This tends to soften the blow of loans, at least to some degree.