In my opinion, this is the wrong way to think about things. You should start at the top of the pyramid to the right and work your way down from there. Not start halfway up and only head down.

Obviously, you need to adjust that number for your country and its' cost of living. And that is not saying that your happiness won't improve, it will just improve less and less for every thousand additional dollars that you earn. Knowing this fact is useful but truly understanding it can be powerful. It is difficult for most to internalize and believe it to be true. But the sooner you do, the sooner you can start to focus on other more meaningful aspects of life. Don't let your financial goals dominate your focus.

The reason life goals in general are important is actually a more difficult question to answer. But the simple answer is: happiness. The journey of life is more enjoyable if you know the destination.