There are 2 different issues, let's not mix them. One problem is scarcity, the other is price. There's plenty of water in Dubai despite the place being surrounded by desert. The problems are in Chad or Sudan where millions live with less than 2$ a day.
No. They are not different issues. There is hardly any natural fresh water available in Dubai, same as the case with countries such as Chad or Sudan. So they have to first desalinize the salt water, and convert it to fresh water. That is why the water is so expensive in Dubai. And you should also remember that the population of Dubai has increased by close to 1,000% in the last 20 years.
And do you have any idea about the population growth rates in Chad and Sudan?