Another discount is through a thing called Daily getaways. They offer a different travel deal every day for 3 or 4 weeks. I think it's in April.
The last few years (apparently... I only found it last year) they've had a certificate for certain Loews hotels, which includes Royal Pacific, to get two nights for $325. After purchasing I received an email with a form to fill out about when I wanted to stay, and emailed it back. Heard back in about a day that I got my reservation for a Fri-Sat in September. If we hadn't been lugging wedding clothes and 6 bags, I would have done as
@gottalovepluto did and stayed somewhere cheaper the first night then gone to check in to RPR in the morning, because your Express Pass is valid all of your checkin/checkout days. Instead we just bit the bullet and paid ~$280 for Thurs night.
They only have so many of each deal each day, though, so you have to be logged on right when they go on sale as it's pretty competitive.