Is it haram for a business owner to charge tourists more money than he would charge locals?

Imam Ibn Baz said: A believer is obligated not to deceive people. Rather, he should seek a fair price that does not harm others. For example, if the standard price for watches is 150 (units), he should sell them for that price just like everyone else. However, if someone insists or happens to be a friend or a relative, and he offers them a discount, there is no harm in that. But if he cheats people—charging more when he sees someone weak or ignorant, and giving the regular price only to those who are knowledgeable or sharp—this is impermissible. He must treat the ignorant as he does the well-informed and sell at a price that is known and fair to all. He should not deceive or betray anyone, but rather sell at the market price like others do, so as not to mislead or take advantage of people.