Suppose a manufacturer sells a button-fastening ma- chine that saves a firm the labor cost of le per button sewn on shirts. Suppose firms differ in the total number of buttons they sew on. The manufacturer sells its ma- chine with a requirements tie-in that requires a pur- chaser to buy all its buttons from the manufacturer. Suppose the manufacturer can install a meter that mea- sures how many buttons each machine sews. If the manufacturer can charge according to the use measured on the meter, is there any advantage to the tie-in? Would it be sensible to outlaw tie-in sales, but allow the manufacturer to charge according to the metered use?