You say the family's religious. I assume you mean Christian. If so, their actions do not show that they understand and are following Biblical teachings. If you really want to interfere, here's a parable that fits:
Have them read the Parable of the Talents. Here it is in a nutshell: The master of a house went away on a lengthy journey. Before he left, he gave each of his three servants some money (measure of money = a talent). The first servant was given a large amount (might've been 10 talents), and he invested the money and saw it increase sharply. The second servant was given less -- let's make it 5 talents. He also used his money wisely and increased it, though not as much as the fellow who started with more. The last servant was given only a single talent. He buried it in the ground, where it stayed. When the master returned quite some time later, he asked each servant to report what he had done in his absence. The master was very pleased with the first servant who had increased his money the most. He also had praise for the second, who had accomplished much with a more moderate amount. The third servant tried to make excuses, saying that he knew the master was a hard man and would be angry if the initial investment was lost. If memory serves, the master called the third servant "wicked and lazy" for his lack of industry, and he took away his money and gave it to the highest-producing servant. Clearly, God isn't against business and earning money -- though in many other places he pushes the need for honesty and fair dealings in business. In fact, it's quite the opposite: He expects His people to work and invest. They may end up super-wealthy like Abraham, or they may live a simple life like Mary and Joseph, but He expects work and increase.
You can also quote Proverbs 31, which describes an ideal woman, and PART of this deals with her financial dealings. Describing just the financial part, the verses say that a good woman works hard, lays in stores of supplies for her family (including colorful, warm clothing for the winter), shops carefully to get the most value for her money. It says she makes investments (specifically it says land, but that could be construed in a more general term for modern life). It says that her husband is pleased with the way she runs her household, others ask her advice because she is wise, and that her family does not have to "fear" the future, for they are prepared.
On the other hand, we can see that the Bible frowns upon frivolous spending. For example, when the Prodigal Son demands that his father give him his inheritance, he runs away and wastes his money in the city . . . and then finds himself begging for a job slopping pigs and envying their food (which would've been the lowest insult possible for a Jewish boy, who would've considered pigs unclean). He didn't choose hard work and saving, and he was punished.
And the Bible discusses putting God first, other people second . . . and money some way down the list. For example, there's a quick description in the gospels of an unnamed "wealthy young ruler" who asked Jesus what he must do to become a follower. Because Jesus knew what was in the man's heart, he knew that the man loved wealth more than he would love God. So he told the man that he must give up all his worldly goods (meaning, put your priorities in order), and the man walked away from Him. This doesn't mean everyone is asked to walk away from money. For example, Kings David had tremendous worldly wealth, and yet he is called "a man after God's own heart". He had money, but he also had his priorities in the right place.
No, I don't think this family has any idea what the Bible actually says about money.
