For fine art photographers? No. It's a matter of want not need for them.
Commercial, products, fashion, architectural, industrial, scientific, yes, and more.
I know quite a few of these who will regularly shoot 400-500 sheets of 4X5 a month. For them a medium format back is a money saver, because after 12-18 months the savings start to escallate.
Add to that the capital depeciation vs the expensing of supplies, the savings of time running back and forth to the lab, the time and energy spent doing high-end scans, and frankly the equaition is a no-brainer.
I know of one commercial photographer who was "forced" by his accountant to buy a medium format back. Once the quality issue was settled the financial ones were so compelling.
I remember the exact same situation with a photographer friend of mine some years ago when the first Canon 1Ds came out at $8,000. We met on a shoot and he was using a 1Ds for the first time. He'd shot film only until then.
Knowing that he was poor as a churchmose, I asked him why he had just spent $8,000. His answer was that since he shoots 20-30,000 frames a year for stock, he couldn't afford not to. He paid off the camera in much less than a year with savings on film and processing, and after that was well ahead of the game. Once he'd accepted that the 1Ds gave him better image quality than film, the financial decision was inescable, simply from a financial point of view.
This is what a lot of Sunday photographers simply don't understand. $10 - $30,000 backs aren't made for them. They can buy them if they wish, and can, but the Leafs and Phase Oness and Imcons of the world aren't after their business. They are selling to the working photographers for whom these are tools, not toys, and for whom these products are capital investments, not things to be hidden from wives.
These products aren't even sold in stores for the most part. They are sold by VARS who will visit a photographers studio, help develop workflow solutions, and so forth. It's a differnt world.