not just Disneyland, but almost everything. The first few times I went to the Disney parks there (incl. the Disney SeaPark) it wasn’t cheap at all, in USD. At the time it was more expensive than the US. Of course, the exchange rate was around 100 per US$ at the time.
It was also horribly crowded back then — not sure if this is still the case. The Japanese have very few kids, so maybe this has reduced demand over time. Also, Disney has opened parks in Shanghai and Hong Kong, which probably took some of the pressure off their Japanese parks, in terms of visitors from overseas.