Alexa has nothing to do with how much money you can make online. The people who buy sites based on Alexa traffic alone are clearly in the dark when it comes to site traffic.
Getting traffic is not hard, the trick is getting people to buy into your product or service. If your site has value in terms of both good quality traffic and a product that people want to buy that is how you make money. If your site has both of these then selling it for a good price shouldn't be hard to do. But why sell it when you can keep the money to yourself?