NIMBY means not in my backyard. As in, I want the benefits of a thing but not its cost. Wanting affordable housing while denying development is NIMBY. Saying no development because you want higher property prices is not NIMBY, it's prohibitionism. (Depending on the environment, it could be reasonable and/or heartless.)
> been told by people who would know that one of Sydney's big problems is that property developers are able to artificially inflate property value by staggering the release of newly developed property onto the market
This is prudent pipeline management. Why would you bid up the cost of materials and labor only to dump the finished product at a loss?
On supply and demand: American house prices are elastic, but over long timelines [1]. In Sydney, dense housing is more elastic than detached housing [2]. The abundance of those historic terrace houses, together with long development approval times, cause the high prices and relative price inelasticity.
[1] https://www.sciencedirect.com/science/article/abs/pii/S00941...
[2] https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-8462....