Obviously density isn't sufficient to create value on its own, but in the context of neighbourhoods of a city, more dense areas tend to become more valuable tha

Obviously density isn't sufficient to create value on its own, but in the context of neighbourhoods of a city, more dense areas tend to become more valuable than less dense ones, because density supports better services. So if one suburb lets developers build high rises and another of similar value doesn't, the former is likely to end up more valuable in the future.