I mostly agree, but I interpret kelukelugames's comment as saying that it's one thing to do your homework and be aware of what you're getting yourself into, but it's quite another thing to actually be living on ramen in your mid- to late-twenties. That is to say, people--especially your typical 22 y.o. undergrad--probably often overestimate their willingness to fully live the life of a PhD/postdoc, regardless of how much they "aren't in it for the money".