I just tried to price adding 1 day at Universal for my August trip to WDW. For our family of 5, we're looking at $1,064 for a park-to-park ticket. This is an estimate based on May pricing because Universal's website won't even let me buy an August single-day ticket right now. My family loves Harry Potter almost as much as Disney, and I'd hate to pass on Universal. But I'm not sure I can justify that pricing as an add on to our trip. It's even harder considering we managed to get our 5-day park hopper plus tickets at WDW for a total price under $1700. I get that there's multi-day discounts and stuff, but the need for a park-to-park ticket at Universal in order to experience the primary reason we're going there (Potter) makes it ridiculous.
I am not trying to turn this into a Universal vs. Disney debate. They both are good and both have their benefits. They also are both expensive. But anyone that claims that Universal is more of a value or that Disney is gouging people while Universal is not is just full of it. Not to mention that FastPass+ is still free, but Universal is asking $79.99 per person for their Express pass. FastPass+ isn't perfect, but it's still included.