From An accompanying table compared costs for five options CASE 1 2 2A 3 4 Payload bay ft 10 x 30 12 x 40 14 x 45 14 x 50 15 x 60 Payload weight lbs 30 000 30 000 45 000 65 000 65 000 Development cost billions 4 7 4 9 5 0 5 2 5 5 Operating cost millions flight 6 6 7 0 7 5 7 6 7 7 Payload costs pound 220 223 167 115 118 It appears that this figure came from Case 5 which is what was built