1) Nobody is doing you any favours if they tell you it is a sin: that is up to you. It is unlikely that any god/s you believe in are going to send you to hell for doing it and, if they do, you will meet the rest of the human race there.
2) It categorically does not waste blood supply, whatever that means. It's actually good for you physically: speeds up your heart (a good workout) and will bring you a sense of peace and calm. And maybe sleep. You will be clearing out your prostrate and potentially helping to prevent prostrate cancer in the future. It also burns up a few calories (but it's not a waste of energy).
3) As for killing 50 million cells: sperm cells die anyway. They don't sit around for 20 years waiting for you to impregnate some lucky woman. Your body wants rid of them, they get ill and die of old age. If you don't masturbate they will probably come out anyway in a wet dream (which will blow your mind).
My advice: get a grip of your little man and work him for a few minutes. If you don't get a lot of feeling grab some hand cream and crack on. Just be ready with a box of tissues because, if you have never had an orgasm, you will probably blow a hole in the wall.
Under no circumstances use washing up liquid / an apple pie / shampoo.
Would you pay less for a humanities degree?