There are a number of organizations that does this free and in my area the city gives you two fixing's a year. the problem with that is it doesn't cover a litter of cats. There needs to be a way to deal with a whole litter.
Also needs to be way to push the issue so as to really help before things get hopelessly out of hand (see my post above). Sounds like that what your 50-cat friend needs. A couple of friends or neighbors or relatives given authorization by a local court to go in take the cats a few at a time to be fixed and returned, even over the objections of the owner. Your friend’s situation sounds fairly typical: lots of people know something needs to be done, but nothing is likely to get done until it reaches a point where animal cruelty charges can be brought.