Wow - that is a very loaded question. As a current broker, and a former licensed contractor, I will tell you, with 100% certainty, that ...it depends. Everything, especially in hillside ordinance areas within Los Angeles depends on the Geology Report, survey, access, and stability of the site. A $30,000 lot in Hollywood Hills? Hmm.... Not buildable without an exorbitant amount of engineering and shoring needed in order to make a project feasible.
Your cost is not in the land, in this case, but rather in the improvements necessary to make development feasible. A very interesting alternative, and possibility for otherwise "unbuildable" sites can be found with a very specific, earthquake, hillside friendly building method that I have worked with recently. There is a site:
that offers pole construction buildings. These are very Japanese inspired in nature, and can be constructed on otherwise unbuildable sites.
When it comes to land - grab your geo-engineer, and prepare to pay for some r & d if you're thinking about shopping in the lower price range for the Hollywood Hills.