The direct costs of back injury is that you can't work for several weeks, but the future costs of the back injury will be much bigger. Your back injury ensures that you will be unable to work in the second part of your life. You need to be supported by the society, directly or in the form of an insurance. Your back injury presses on your direct neighborhood. The society will pay the costs of your back injury.
Your back injury will give you less joy of life. Once felt the problems around your own back injury you wishes you had never lift too much. That's why I can tell you: don't lift goods by hand. Use devices or don't lift. Your back injury is a problem for you, me and everyone.