While I admire the quality of the lens I can scarcely imagine a full time pro wanting to buy one. Manual focus for what is a portrait lens seems to be a recipe for frustration.
I'd only get one if I were a full-time professional and using a Nikon D810.
The other reason a pro would not buy it is because $4500 is a lot of working capital tied up in a tool that no client will appreciate.
Yeah it does seem like a poor business decision. I guess you could make that money back if you're one of the top pros earning thousands per job. For the average working person it's like 2 months salary for almost no gain in extra clients or work. Don't forget you have to insure that bad boy too!
I have a feeling Sigma are going to bring out an updated Art version of theirs soon at a quarter of the price and 99% of the IQ. The current one gets the job done as it is for most folk looking for an affordable 85.
Yes, you have to GRADUATE to this level of lens. If two month's salary is $4500, then you haven't reached that level. I don't even know serious, semi-professional photographers who earn that little. That's where I'm coming from.
In that context, I'll say again that this lens is for the full-time professional, wealthy amateur or those maniacal enthusiast types who rather take the bus than buy a car to afford this lens. Especially love that last category of folks.
I know full-time pros that need to budget for that super-lens. Because they are reaching that level in their business when they need the performance, functionality or durability that lens will give them.
And at that level, $4500 is simply another business expense. Laptops, computers, advertising, marketing, health insurance and other expenses are all going to cost as much if not more than that lens. Hell, most professionals I know who use a cell phone for business have a monthly bill at least $100/month. If you stop your service after 4 years, you got a worthless piece of plastic. But you still have a lens. And since I insure my gear, I can estimate that insuring this lens will cost about $5 - $7/month. That's a cheap lunch.
And for portraits, AF is a convenience. Even if you're shooting at f1.4, AF isn't going to nail focus much if any faster than manually. And at that aperture, your AF is going to hunt for focus every time you press the shutter. MF isn't. I'm cool if someone likes AF. No problem. But I've been MF for my fashion and portrait work, forever. I don't miss it. "Recipe for Frustration"? If you have really bad eye sight and don't have glasses. Yes, I guess it is.
Lastly, even if I were at that level to afford this lens, even if I shot with a Nikon D810, I don't know if I would get this lens. Detail is AMAZING... And if you do lots of close-ups, it might be worthwhile. But as I mentioned numerous times on canonrumors.com, my Canon setup is sufficient until I can graduate to Medium Format. Because 'the look' of MF is more important than pure sharpness. Unless Canon comes out with a sensor that can give me that same look, possibly with that 5-layer sensor that they patented recently, that's my plan.