Aren't Christians peddling a cure for a disease they just made up?

Christianity purports to offer salvation from the consequences of sin and the falleness of man but it's only because of Christianity that one has any notion of "sin," much less any worry about eternal punishment for it. Do you really believe a god made the first man and woman in a garden and damned them for all eternity because they ate a piece of fruit without permission and realized they were naked? Would you throw your child in an oven for eternity for taking a cookie without your permission? Should you really trust any organization trying to sell you a cure for an illness they infected you with to begin with?