I was brought up in the journalist tradition that film was cheap, not necessarily because it was cheap, but because the alternative was worse, when you start to become obsessive about the amount of film used your whole output becomes compromised.
Penny pinching film nowadays should mean you just go straight to digital, and not let fiscal matters affect your photography. But I wouldn't expect a better or worse hit rate with either. If I shoot three films I am happy as a pig in muck if I get three images I can happily stand by for the rest of my life. With digital I may shoot more, but my hit rate is just as refined, I mistrust my judgement if I find more more than just a few images that seem acceptable from three hundred exposures. So film is never wasted, even if nothing is worthy of reproduction on a roll, it means you learned something, you learned a lesson in failing, and that is often more important than a lesson in winning.
The problem is that quite often what comes out of the developing tank is nothing like as brilliant as what you saw in the viewfinder. I've had shots which ticked all the "rules" off but were best described as "meh" when developed.
As for wastage, this annoys me with later bodies. My Super A insists on winding and shooting three times at the start of a roll before it will meter properly or allow you to select a shutter speed, meanwhile with a KX I can shoot frame 0 onwards and get at least one more exposure. The AF bodies are even worse for winding through film leaders before they'll let you shoot.
The backing paper on 120 film I salvage and use as notepaper in my messenger bag when I'm on commuting trips. In the lab, this same backing paper is described as a "significant waste product in volume". The other waste is the plastic spools: I've seen a mountain of them in the corner of the E6 lab. There does not seem to be a recycling method for them (?).
Sprockets and nice thick, strong film base make for film that advances easily and quickly, is easy to handle, and sits very flat, allowing for precise focusing.
I think 120 film would be great if it was made the same way, instead of with a paper backing.
“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”
Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2
Still better than using digital. And, if you are really worried about waste, many of the elements of film and analogue photography (including 35mm) are easily recyclable or cheaply reclaimed using existing infrastructure.
You forgot to include the something like 5-mile leader and trailer used in the manufacturing process. I think this leader can be reused, but I'm not sure how many times, and the length of the leader depends on the size of the manufacturing line. Of course all film requires this, but it's even more unused film area.