You're probably going to get a lot of different answers back on this simply because "expensive" is such a subjective issue. Us personally, I don't like to spend more that $100 a night unless we're doing a big trip. This usually means we stay at one of the Best Westerns (can't beat the military rate) and then just use the ART.
I'd recommend maybe using hotline (I think thats the one where they don't name the hotel) and see if you can get some cheaper prices. Good luck!
We'd need to know what you were looking before. Were you looking at the motels across the street, the resort hotels, or the convention hotels? When are you going and who is in your party?
These are our go-to inexpensive hotels - nothing fancy, but the prices are good and you can walk to the park. I prefer Quality Inn, mainly because of the breakfast and super nice staff, but Anaheim Plaza's pool is much bigger.