If the price of salt increased, demand would largely be unchanged. It is only a small % of income and people tend to buy infrequently. It is a good with no real substitutes at all.
Bought very infrequently, diamonds are the ultimate luxury with few exact alternatives. You could buy other precious gems, but others may not have the same allure as diamonds. A cut in price wouldn’t increase demand very much.
The Apple brand is so strong that many consumers will pay a premium for apple products. If the price rises for apple iPhone, many will continue to buy.