The real saving comes in when you shoot colour trannie and it is huge!!!!!!!!It is the processing costs that kills you.

5x4 Velvia quickload - 2.50 plus processing 3.50 = 6 So for each image, I conservatively assume you shoot 2 sheets (OK sometimes your exposure will be perfect, but you will still process that second sheet for a spare or for a teensy weensy tweak. Equally often you will very much need that second sheet for push pull. Therefore your cost per image is approx 12 minimum assuming you do not actually shoot 3 differently, processing the best guess first and then doing the others....

A roll of 120 is 2 mail order and the same at 3.50 to process = 5.50, so half the price for 2 different bracketed images (3 frames per image, 6 frames per roll)

The cost for 6x12 120 is therefore 2.25 per shot and 12 per shot on 5x4 quickload. Thats 10 per shot saving, again assuming that you do not even bracket on sheet, but do a second exposure only.

10 x 30 images =300 ie the cost a second hand Horseman 6x12 back. Plenty of people would shoot that in a 2 week photo holiday, or for a pro doing holiday resort shots or architecture/interiors (for example), a few days....

I agree tho that for mono, its crazy, which is why I dont hve one. also, it is yet more weight to carry.