"Dear" or "not dear" is the general way people refer to the cost of things in any part of the Bruitish Isles I've been to. Probably more common than "expensive", and I donb't thinbk anyone would be likely to say "costly". The other way might be to say something is "a bit much", or "not too much" and so forth.

So Americans would be likely not to use "dear" or understand it? How about Australians?