On the economics of MF digital capture...
First, I think you really need to compare 4x5 film to MF direct capture for 'detail' equivalence. If you do the math for sheet film, the per shot costs go up significantly especially if you cannot develop it OR scan it for yourself.
I might disagree if 6x7 were used with a high-end setup like the Mamiya 7ii, but let's go with 4x5. Of course, in my previous post I was just pointing out the thoughts behind why I decided not to buy a D700. The price point of MFDB is entirely outside of any personal feasible limit for me (recently married in graduate school with my wife about to also enter graduate school).
Note that a good MF film scanner will set you back $2000 minimum, and a good 4x5 scanner will start used at around $3000. Used drum scanners can be had for around $3000 or $4000. New Imacon X5, as much as a used BMW X5
D). With any of these you'll be lucky to complete 6 scans per hour on 4x5. Service bureau scans of 4x5 are pricey -- $50 to over $100 for the best.
I have access to the following scanners on a daily basis, the Canoscan 4000 previously mentioned, Nikon 8000, and an Imacon X5 plus a handful of Epson flatbeds like the Epson 700, 750, and 10000XL. Additionally, I can get drum scans at a fraction of the price you state, but this is due to a friend having an Aztek drum scanner. I can wetmount to my Epson 700 (of course, mine was free as the lab couldn't use it due to a dead pixel, but it's outside the frame of a 4x5 so it's not an issue) using a piece of sheet glass with a brass reservoir glued to it to make it easier/cleaner to fill, some 3M extra delicate tape, mineral oil (though I'm switching to Kami just because it cleans easier), and 4 Sacagawea gold dollars which place the scanning plane at the best plane of focus for my 700. At 2000dpi (which is within the optical resolution of the 700) I get a 20" x 25" file @ 360dpi. Since the majority of my work is palladium printed with digital negatives I don't need/can't handle a print larger than this anyway so this is a perfect size. Most of my work from 4x5 is 12"x15" or 16"x20". If I were going larger I would scan them on the Imacon. So far we're looking at $700 for the 4x5 scanner with the piece of plate glass, brass shims, $4 in coins, and mineral oil being negligible. Also, I still have my original that can be rescanned at a much higher resolution on an Aztek @ 8000ppi if need be, but I don't need that big of a file anyway.
Scanning costs aside, a sheet of 4x5 color tranny or neg emulsion will cost around $3 for load your own, or $4.50 in readyload trim. Add $4 per sheet for lab processing PLUS mailing costs if there is no local lab.
But you're talking color. I shoot solely b&w where the cost is $90/100 sheets of FP4+ so it's ~$1/sheet and I process at home in a Jobo expert tank on a unicolor roller (say $350 for this setup, though I just kept watching on eBay until I found one for $150). I develop in homemade Pyrocat-M and make my own fixer from scratch, so processing is on the order of pennies to develop 10 sheets in the tank. So $350 to get the stuff to develop and tack on an extra $100 which will make enough chemistry to last years, so we're at a total of $1150.
Finally, if you do all this for yourself, add something in for the time you spend, unless it isn't worth anything to you
I think this isn't even an issue as I am not a professional in the sense that I must make/sell work to provide for my family, I have a day job. Photography is my escape. Do you tack on the cost of your time to the price of a ticket to the movies? Unless the work your making is part of a business plan I think this part of your argument is an argumentum ad populum fallacy for most people because photography is their hobby and a hobby by definition is meant to be a leisure activity.
Now, don't forget to amortize that digital back over three to five years, and remember it has residual value at the end of that period. So a new $20,000 back today should still be worth at least $5,000 in 3 years and probably more, so your sunk cost for the DB is about $5K per year REGARDLESS of number of frames exposed.
Seriously, how many of you are still using the same digital equipment you purchased 3 years ago? Additionally, all of the files shot with equipment shot now cannot be increased in quality while I can always have my 4x5 drum scanned at a later date or on an individual basis if I need a 40" x 50" print. Plus, scanner prices are dropping--I see a Creo or Eversmart in my future at some point for under $1000.
Using the 4x5 example above, you average $8 per sheet for film and processing. Forget your time, and thats about 600 4x5 film frames per year to break even with digital -- I'll shoot 600 frames a DAY on some shoots! (In fact, I suspect I'll average over 200 frames per day on our Moab workshop alone, and I'll be teaching much of the time!) Factor in even $10/hour for your time spent scanning, and it is significantly fewer to break even.
With my example it's $1150 for the scanning and processing equipment/supplies, $800 on my camera, $250 on my lens (135mm Sironar-S MC f/5.6), say $150 for the 3 grafmatics, $150 for my Harrison Changing Tent, and say another $150 for random things like a loupe and dark cloth and such, though that's probably overestimating. The tripod is a wash as you'll need one either way. That's $2650 and for me it was really only $1950 as my scanner was free. Now if we go with the cost of $5000/year I can buy everything listed above and still have $2350 to buy 2,350 sheets of film for that year and even if there is an outlay for some extra consumables you could still easily say $4000 for 4000 sheets every year after that with $1000 in the coffer. I don't shoot 4000 sheets of 4x5 in one year and I doubt I ever will because a very productive day for me is all 18 sheets in the grafmatics or one some occasions I'll do 36. I could shoot 3600 sheets if I did 36/day for 100 days, but that won't happen because I have a day job as many others do, too. My keeper ratio is also very high as I will scan/print about 80% of my 4x5 shots and I'll just make the crass assumption that you don't print all 600 images you're shooting. Additionally, the cost for me to add more lenses to my system is dramatically reduced compared to the costs for a MFDB, a 210mm f/5.6 APO Symmar-S at Keh.com in EXC condition is under $500. Finally, I LOVE shooting 4x5. Yes, you could go the technical camera route, but then that's NOT the same as composing on a complete 4x5 ground glass; as a matter of fact, I have 75 sheets of 8x10 coming that I can wetmount to the Epson 10000XL, scan at 2000dpi and get a 40" x 50" at 360dpi without even trying hard--not the goal, though, I'm doing portraits with big, old brassie lenses and contact printing them in palladium.
Obviously, these are the numbers I came up with for me and they don't really apply to others, but I thought I would just go ahead and throw my thoughts into the thread.