Nothing in my post is suggesting the Roman Catholic practice of buying and selling indulgences. That is foreign to the biblical doctrine of heavenly rewards for the faithful Christian.
One does good things from gratitude to God and from compassion for one's fellow humans, not for thought of reward. To teach others to do things for reward or to avoid "peril" is a bad path to put Christians on.
Of course, the Christian's good works flow from his gratitude to God, and his compassion for his fellow human beings. Nonetheless, in His grace God has chosen to reward faithfulness and self-control in stewardship and service, those who overcome trials and temptations, those whose refusal to deny Him under pain of death results in martyrdom, and other circumstances that please Him.
The fact of rewards does not paint everything the color of money, so to speak, for the Christian. It is simply the idea that we want to be well-pleasing to our heavenly Father. The irony of this doctrine is that any Christian who would choose to operate on the crass level of doing good deeds so that he can put another notch on his "reward belt" is in fact going to forfeit any reward he might have otherwise received, because his motivation is wrong. Remember, God looks upon the heart, and the Lord weighs the motives behind our works.
Yet God will indeed reward Christians in some way at the Bema Seat. Certainly this is an exciting truth that must have a place in the Christian's motivation for service. The desire to please God by striving to serve Him in a divinely approved manner and motive, knowing that He will reward such faithfulness, is not wrong. As a child at home, or a student in school, most of us have experienced the same thing. I can recall a 5th grade teacher of mine who gave extra credit to students whose homework assignments were neatly done. If you were careful to use good penmanship and organization, you would earn what she called a "V.N." (Very Neat) and if you got 10 of those you were exempt from one homework assignment. I liked this teacher and wanted to do my best in her class. It's like that with God...we should want to do our best for Him, and He has graciously provided extra incentive for us to do so.
If such beliefs give you motivation to do more good than you might have otherwise, verily you have your reward.
...the joy of the good thing itself and the good it brings about is the real reward.
I Corrinthians 13: 11