Regarding the number of 50+ class students at Stanford, I have have taken classes in numerous different fields there. My experience was that Stanford rarely offers more than 1 of a particular class per quarter, but has a large number of sections with much small sizes, where more individual discussion occurs. That 1 large class is often taught by a well known figure in the field who wrote the textbook and whose research relates to some of the core class concepts. This system results in the more popular low-level prereqs often being quite large, in some cases hundreds of students that can fill up an auditorium. The larger classes include the basic class level (other slower/faster/more rigorous/more eng focused/different levels of these classes available, which are not as crowded) intro chem, bio, physics, and math, which are prereqs for pre-med and types of engineering, as well as some of the more popular general humanities type requirements for graduation, and other low level classes that are just generally popular such as intro CS classes, intro to statistics, and intro psychology. Upper level classes that were rarely taken by people outside my major almost never had 50+ persons because my major did not have 50+ persons in it. You can estimate the size of specific classes by looking up the number of sections at https://explorecourses.stanford.edu/ . One might roughly estimate 10 persons for section, so classes with 5+ sections have 50+ students. So a particular student might have most of his classes 50+ or hardly any, depending on his major and the specific classes he chooses to fulfill his major.
As a specific example, one of my most enjoyable classes was an intro bio class taught by Robert Sapolsky. I’d encourage anyone to read his books for fun, which were texts for the class. They include stories about things like studying baboon behavior in a wild African environment, then darting them and measuring hormone levels . The books have great reviews on Amazon from laypersons with little bio background, as well as experts. He’s also a really great lecturer, and has won numerous awards including a genius grand and the Carl Sagan award for science populization. All students who take intro bio get the opportunity to take Sapolsky’s class (or at least they did in my year), rather than splitting the class into a large number of smaller subclasses, taught by less experienced persons who would likely provide less of memorable experience. Grad students lead small sections after the class that discuss the lecture and give the opportunity for more of an interactive group discussion about the concepts. The same concept can apply to other special opportunities, such as Mark Zuckerburg guest lecturing in a popular intro CS class. Everyone gets to see Zuckerburg’s lecture about the class concepts instead of a lucky few.