On the other hand, you might have more in the place with higher average income. Remember that buying isn't the only way that you can get things.
Compare NYC with North Dakota. Things cost more in NYC than in ND, which is bad if you're buying, but there is a lot more free stuff in NYC than ND.
Plus, there's more opportunity to move up in NYC than in ND. In some cases, that opportunity is worth something.
Yup. Great museums are cheaper in NYC than ND but owning a horse is much cheaper in ND.
Plane tickets between two specific locations are world price, but you also have to take where you live into account.
For example, going to Singapore from Reno costs more than going from SF or San Jose.
Of course, this is counterbalanced by having more opportunities in terms of career, education, culture, and entertainment.
As to effectiveness -- that is dependent on your personal goals. Some people are very effective at chilling out and not doing much. Others are very effective at building business, or playing a sport, or programming, or whatever. Dependent on what you want emulate the ones succeeding in that and you will be "effective"
b) Some people get more enjoyment being more rich than their immediate community than just being rich. This is true for everything else apart from money. Some people want to have more knowledge than others etc...