Nobody just shoots a digital camera the equivalent of a roll a week for just a few years.
Let's do some math, shall we?
Let's shoot us some Arista Premium 400... It's re-badged Kodak Tri-X. It's $2.59 for a 36-exp. roll. Shipping from Freestyle is $5.99 for a small order. If you buy 4 bricks of film, that's about $0.15 for shipping per roll.
-One roll of 36-exp. B&W film : $2.74
I've found it costs me about $2.50 to process a roll by myself (a bottle of HC-110 processes a hell of a lot of film)
-Developing costs for one roll: $2.50
-Total cost to process one B&W roll: $5.24
-Cost per exposure: $0.14½.
By comparison, buying color film and developing it at my local Walgreens is about $16 per 24-exp. roll (try finding 36-exp. film in a drug store in rural America).
-Total cost to process one color roll: $16
-Cost per exposure: $0.67.
Now, let's look at some digital cameras:
Nikon D3200… 14.2mp DX format, $476.95
Nikon D600… 24mp, $1,996 at B&H
Leica M9… 18mp, $6,495 @ B&H
Now, it's time for some more math.
How many frames would I have to shoot to “break even” — i.e.: How many frames to see a cost savings in not developing my own film?
Nikon D3100: 91 rolls, or 3,275 frames.
Nikon D600: 381 rolls, or 13,719 frames.
Leica M9: 1,239 rolls, or 44,622 frames
Now, how about color film at Walgreens?
Nikon D3100: 29 rolls, or 715 frames.
Nikon D600: 125 rolls, or 2,995 frames.
Leica M9: 406 rolls, or 9,742 frames.
If you shoot one "roll" of color a week, the Leica will pay for itself in about 8 years. In black and white, that's 24 years.
That said, let's look at a realistic load of digital images... I can shoot 100 frames in an afternoon without problem. Let's say I shoot 250 frames a week. That's just shy of 7 rolls a week in B&W and 10 rolls of color.
In B&W, that's 3 years and five months. In color, that's a year and two months.
I'm not even touching lifespan, even though a MTBF of 250,000 frames means a Leica M9 will "die" after $167,000 in color film.