All excellent points. My understanding is that fee waivers are granted more or less automatically for any plausible candidate, and no school would ever take anyone to collections over a denied fee waiver request (they just wouldn't process the application until the fee is paid), but as you point out, low-income / first-generation-college applicants are unlikely to know this stuff. There are also programs like QuestBridge which attempt to streamline the process of applying to multiple schools, fee waivers, etc., but again a lot of students don't know about them.