XYZ stock is 100. A "natural" call fly would be 100/110/120 (+1,-2,+1) say it's a 5.00 debit. Say the same put fly is 4.50. Both of these have three legs. The iron fly is 100/110/110/120 (+1 put, -1 put, -1 call, +1 call) is a 4.75 credit (which is 10-4.75=5.25 debit). All of these are...