We wanted to go to both parks on 12/21. At first, the price was $419 for HRH and $459 for PB. The 2+1 day free park to park passes from
Undercover Tourist are $152. Total price: $608 for passes plus $419 (plus tax and parking) for hotel. Over $1000 all in.
I discovered that I could buy a $199 annual pass for one member of my family - and use the annual passholder code for the hotel, which brought HRH to $209. Total price: $665 for the passes plus $209 (plus tax and parking) for hotel. $874 all in.
I feel like I am missing something, but I think it works - leaving me $125 or so for butterbeer.