They bill, expecting to be told that no, the procedure/item is worth x,y,z and then take the difference between what they bill and what is paid AS A LOSS on their corporate returns. This is especially true when things are billed onto Part B. Usually Part A billing is close to what Medicare approves. But part B (office visits, lab work, outpatient surgery) have the huge gaps. Another reason why more and more procedures are now "day surgery" not overnight, so considered part B.