OP I'm afraid you're going to be stuck with good old-fashioned legwork How many people are you really talking about in total? You surely don't truly need to literally find pricing from all of the several hundred US airports with scheduled commercial service.

I get that sometimes cheaper fares can be found by checking different airports in a local region, but for narrowing down your plans just start with the closest or most logical airport for each friend, then for those outside your budget parameters do a more detailed search or something like that. Even if you're talking 15 people it won't be all that cumbersome.