Answer: Cover your costs
If the marginal cost of producing a bracelet is 25 cents, then this means that it takes you 25 cents to create one bracelet. This includes material, as well as any other resource that might be employed (such as electricity, time, etc.). If you also sell each bracelet at 25 cents, then this would be enough for you to be able to cover your costs, but not enough to be able to make a profit.