Serve God or Mammon?

According to Eaton Bible Dictionary, Mammon is a Chaldee or Syriac word meaning "wealth" or "riches." It is also used as a personification of wealth, the god of riches. Luke 16:13 No servant can serve two masters: for either he will hate the one, and love the other; or else he will hold to the one, and despise the other. Ye cannot serve God and mammon.
The parable of the rich fool

The parable of rich corn farmer (money changer).

Luke 12:16 Then he told them a parable: "The land of a rich man produced abundantly. 17And he thought to himself, 'What should I do, for I have no place to store my crops?' 18Then he said, 'I will do this: I will pull down my barns and build larger ones, and there I will store all my grain and my goods. 19And I will say to my soul, Soul, you have ample goods laid up for many years; relax, eat, drink, be merry.' 20But God said to him, 'You fool! This very night your life is being demanded of you. And the things you have prepared, whose will they be?' 21So it is with those who store up treasures for themselves but are not rich toward God."

What are Christians to do with their wealth?

David Teniers, Flaemische Kirmes (1640)

Aert van der Neer, Winterlandscape (circa 1650 AD, probably in Amsterdam), Gemeldegalerie, Berlin.

Our income will first be used for our survival. Our physical bodies are temporary vehicles in which our souls reside. They need sustenance and good maintance.

Jesus taught us to pray first that Father's will be done on earth, and then for daily bread. Thus, it is OK to use our income to buy basic necessities and comfort. Of course, one can argue what constitutes for basic necessities, but we can leave this question to each individual's judgment.

Jesus taught a rich young man that the rest, whether it is greater or less than 10% of our income, should be used to help the poor, our neighbors who are worse off.

Jesus did not say that faithful tithers can keep 90% of their income and still follow him.

 We either follow Jesus all the way to Heavenly Father in Paradise, or else.

What then is the point of working hard and making money?

History: According to Angus Maddison (University of Groningen, 1999) in his article "Poor until 1820," the world economy was stagnant and per capita income of the West was about $1200 until 1820. After the fall of the Roman Empire in 476 AD, the West entered a recession that lasted about a millennium. During this period, per capita income of the West was no more than $500 (in 2000 constant dollar). After the industrial revolution, due to mass production and trade, per capita income began to grow. Without a time machine and traveling back in time, it is impossible to meausre income levels of average persons who used to occupy the same land a few hundred years ago. Here are two paintings that suggest that per capita income of European farmers was no more than $500 even 400 years ago.

Present: During the 20th century, per capita income more than quadrupled despite two world wars. In 2002, per capita income of Norway, the US and Japan were $42,000, $37,000 and $32,000, respectively. True, there are many countries that in povery ($1200 or less), but the number of poor countries is shrinking fast.

Future: During the 21st century, per capita income is expected to more than quadruple in real terms. How will it alter our lives?