$7k is actually on the low end nowadays :). I was as surprised as you, but talking to my friends, salaries seem to have shot up this past year. Dropbox, Google, FB, all pay over $7k, some well over that amount.
(samples: Microsoft, Mozilla, Apple)
Even if not in Seattle, the difference between $6k and $8.5k is negligible for a 3 month internship relative to your life earnings.
However, It's only negligible if it doesn't correlate linearly with a starting salary.
If my starting salary is 20% lower at Amazon than anywhere else, you can bet I won't be returning after my internship.