I doubt you'll be able to get discounted tickets to "The Lion King" on Broadway. It's one of the hardest tickets to get on Broadway, and I haven't heard of any discounts for it over the years. I will say that if you can get tickets, it is well worth the $100 ticket price. I see a lot of theatre, and I think it's incredibly over priced, but this show is worth the $100. I know it's a lot of money, and not everyone can afford it, but it is an amazing show.
As for "Beauty and the Beast," sometimes Playbill.com will have special rates for it (although they don't have one now). You may want to try TKTS (the half price ticket booth in Times Square) for this one. I believe that they sometimes offer discounted tickets for this one.
Karen