> Maybe they won't pay a higher salary immediately than to a 30-yr-old, but they'll give you a reward later if they can see how much you helped them

I don't think most companies behave this way. Maybe at one point they did, but I find the reward for doing great work is "That's why we hired you"

Yeah maybe you get a yearly raise and a bonus but it never is big enough to make up for taking a lower salary