I think this question is the easiest one in economics, let's look what Albert Camus says about it ;
'' You don't have to work if you have enough money so that money buys the time. You can do things to make yourself happy in the remaining time. So money buys the happiness.''
Yes, money can buy happiness but up to a point.
Let's think two people, John and Steve. John is the founder of famous football team, he has 100 billion dollars and Steve is the teacher who works for 2000 dollars.
Then we give 500.000 dollars to both of them, who gets happier ? Of course the answer is Steve. Because of 500k dollars aren't too important for John, he has 200 times more money. But its important for Steve, and Steve can use this money for his private and business life, can invest.
Therefore he will has more money and resources, this resources can increase his enjoyment of life.
If we analyse it with using macroeconomics, if GDP per person doubles then happiness scale will increase thanks to money.
So finally, more money = more happiness however,
John + 500.000 $ = +0.1 happiness
Steve +500.000 $ = +10 happiness
''As a result, the purchasing power of money is different for everybody.''