Too be honest, I really don't see why this matters. The banks all pay the same, I know that for fact.
figured there's no harm in asking
I think it's fine that you asked! Us, that is. Don't ask recruiters
Of course, in my world, you're asking so you can better manage your spending plan, not because you'd go for an internship because it paid well!
Many schools will post this info - at least Duke does: http://www.fuqua.duke.edu/career/recrui ... report.pdf
Last year's interns made between $1300 and $12000 (domestic). Median salaries by industry range from about $4k to about $9500.