$3100 if you go to a good school.
$500-$750/wk for the less exalted.
Um, no....unless it was only a few hours a day. 
We're talking about summer between 2L & 3L, right? If we are, the high numbers are realistic for only the upper echelon, the well-connected, and maybe a few people who are very highly motivated despite their average grades/school. Run-of-the-mill 2L summer positions - the ones most law students have and don't talk much about - pay $15-20/hr maybe with some regional variance. After taxes/ss, they clear $500-$750/wk or so for fulltime work. Students outside of the very best schools and without excellent connections should not count on making much more; very few of them will. Of course, that doesn't mean that it's impossible and that you shouldn't try.