You can use your term sheet to talk to your firm about fees. Your VC will have a number in the term sheet to address their legal fees. Your should be somewhere in the 1.25-1.5x neighborhood of that number. More if your books aren't organized and your records are all over the place.

$30-$40k is probably right in a lot of cases (if you touch HIPAA, Crowdfunding, Bitcoin, issues you'll need to bump those numbers up).