The cost is about the same and can be even less actually. Plane tickets may be more depending on if you fly,where you fly from,that kind of thing. Passports are way less than disney tickets, and a one time every 10 years expense. (That money can then go to the extra for plane tix in this equation)
You can stay in a deluxe hotel in another country for waaaayyyy less than a deluxe hotel at Disney. Obviously this depends on the country, if you go to Dubai it's going to be a lot,but most deluxe hotels i've stayed in are often less than say a deluxe club level room at the Polynesian. At WDW the deluxe hotel prices are mainly based on location.
I just got back from Amsterdam last week (for example) and stayed in a suite in a deluxe hotel chain in the center of the tourist district for less than i pay the poly every year, that's for sure.