With 30-bit workflow you can’t actually visually see that many gray value distinctions on a display nor can you address them individually in Photoshop. So it’s a workflow rather than a procedure. On Windows which supports 10 bits per channel it is possible to buy a display and run it at 30bits if the display and your video board have 10 bits per channel output. But, from Photoshop perspective you have only 256 gray levels if your originating file is 8 bit and still have only 256 gray levels that you can [B]edit within the Photoshop toolset[/B] - even though a 16 bit originating file has 65,535 levels. While the image file has them - you can only use tools that edit 256 Luminosity values. [B]Hope that makes sense[/B].
So what you are really asking is the value of using an 8 bit or 16 bit workflow using a display that has 30 bits.
A 30 bit display and its calibration is part of an investment - and is probably way overkill - especially if the display is designed for 4K or Video. You would be better served investing in a hardware capable calibrator display such as a NEC PA series or an Eizo CG series where the calibration is to the display rather than through software to your video board.
If it is not a hardware capable display - then calibration actually cuts down the video output of your video board and that should be avoided. You CAN NOT use Spyder or Munki or EyeOne software to calibrate a hardware capable display. Those packages only calibrate video boards and necessarily therefore - cut down on the fidelity and output. The PA and CG connect the display to the computer and their own software actually calibrates the 10-14bit video engine internal to those special class of displays. I just bought two additional 30" NEC PA301 displays at $749 each refurbished. A killer deal… They appear ever so often for resale from about $1100 or lower. They retail near $2,700. The 27" and 24" appear refurbished more frequently for sub $500. Run away from a new Retina display. Too bright. You need a display that can be calibrated to spec at a very dim output so that it matches “paper”.