Basically, the cost of safety programs is financial -- they cost money to implement and they take away productivity. They cost money because you have to buy new safety equipment, hire people to train your employees in using the equipment, etc. They reduce productivity because workers must take time to learn them and because they generally cause workers to have to work more carefully and/or more slowly.
The benefits are to worker health and perhaps worker morale. If you work at a place where people get injured all the time, you will likely feel unhappy and not be very loyal to your firm. By solving these problems, safety programs may actually help a firm economically by making its workers happier and more productive.