The short answer to that, emphatically and definitely, is yes. Not only is God concerned about the material well-being of Christians, he's deeply and profoundly concerned for the material well-being of the whole world. God created a material world. He created man as a material creature with profound material needs. All we would have to do is go to the Sermon on the Mount to see Jesus' great expression of compassion for those who are in material want. There's a tremendous emphasis of concern in the New Testament that we as Christians have a profound care for those who are hungry, poor, naked, and homeless. That concern indicates a concern for the material welfare of people. The New Testament has a lot to say about wealth and poverty and the various causes and circumstances involving those conditions.
There are frightening warnings to the rich, for example, particularly those who would put their confidence in their wealth rather than in the benevolent concern of God. In this regard Jesus says, "Take no thought for tomorrow, what you should eat, what you should drink, what you should put on; but rather, consider the lilies of the field that they neither toil nor spin. Solomon in all his glory is not arrayed like one of these." He is saying that we can become so preoccupied with the accumulation of wealth that we miss the kingdom of God; we have a concern for the material things to the neglect of the spiritual things. Because we see the world preoccupied with material things and woefully neglecting the spiritual, we may be inclined to become extremists in the opposite direction and say, "All that God cares about are spiritual things." Again, a balanced view of Scripture will prevent us from coming to that conclusion, because there is nothing wrong with a concern for material welfare.
In another manner of speaking, God cares for people, and people are material creatures who require material things in order to survive. If God cares for people, obviously he cares for their material well-being. Health and healing from sickness are material matters, and so God's concern for our health is a concern for our material well-being.
From Now - That's a Good Question!
by R.C. Sproul
Look at it another way, if you wish: while the Gospel is free, getting it out isn't. People have to be paid, materials must be purchased/published/printed, etc.
As the Bible says, "Let the elders who perform the duties of their office well be considered doubly worthy of honor [and of adequate financial support], especially those who labor faithfully in preaching and teaching. For the Scripture says, You shall not muzzle an ox when it is treading out the grain, and again, The laborer is worthy of his hire." (1 Timothy 5:17-18, Amp.)
So yes, of course God cares about our well-being ... and that includes our relative level of prosperity. But chasing prosperity is NOT what we're supposed to do. He blesses us so that we can be a blessing to others, and NOT to consume it ourselves.