With Universal opening up more on-site hotels (Cabana Bay, Sapphire Falls) which don't come with Unlimited Express Passes, they have been increasing the price of the 3 hotels that do have the Express Passes. Also, I've noticed that the Royal Pacific has been hosting more conferences which means they don't have as many of their lowest level rooms available.

With that said I've found a few ways that can reduce the 'per night' cost. One is to get a Universal Season Pass. Any of the season passes, including their lowest cost Power Passes, will allow you to use their Annual Pass Holder (APH) discount. Unfortunately, that rate can sell out fast and thus quite often you won't find it available.

Another option is that they offer nicer discounts for longer stays. I think I've found the best 'per night' cost to be for 7 night stays even in January. I currently have a stay planned with my daughter for January 17th-24th. The 7 night rate is about $168/night. The 6 night rate is $195/night. The 5 night rate jumped up to the $260/night range. Unfortunately for you, it looks like you might not be able to go for a 7 nighter.

I don't know the days you are planning on visiting the parks. But there are some other options to think on. The Cabana Bay hotel can be very cheap. I can normally see rates as low as $100/night and with some promos have seen it as low as $80/night. While you won't get the Express Passes staying there, you will get early park entrance. This means you can hit the Harry Potter section before the masses come in. So you hit it with early entrance and then right as the park opens to the general public, you hit the popular rides in the other parts of the park while the general public is running straight to the HP section.

Also, the weekends, Fri/Sat/Sun, tend to be more crowded than week days. So if you make your "long weekend" into a "long week day stay", no Express Pass might not be as big an issue.