Your missing the fact that you earn more then 14 HH per $
As a diamond member you earn additional 10 HH plus other promotions.
True
Breakdown is 10 points for base stay
but they cap you at earning on any stay 100k base so even if spend 50k only getting points for 10k of spend
You Will also get 10 points for being diamond
As well as what we the hilton promo at the time is (currently till Jan it's double points but if use a Hilton amex it's triple so it's 54 points per dollar).
So let's say it's a double point promo (they have not announced q1 promo yet so this is just an example) you would earn 30 points (20 base + diamond) per dollar plus the 14 points from amex (which is not capped) so if my math is correct you would get 300k hilton from stay + 700k from amex + sign up bonus.