Apple partners with LG to make new 4K & 5K UltraFine Displays
Briefly mentioned during Thursday's press event was an Apple partnership with LG on 4K and 5K monitors, designed with the specifications of its new MacBook Pros in mind.

The UltraFine 5K Display.
The LG UltraFine 5K Display measures 27 inches, and supports resolutions up to 5120 by 2880, as well as the P3 "wide color" gamut. Perhaps almost as important is its use of Thunderbolt 3, which can power both the monitor and a MacBook Pro via a single cable.
Also present though are three USB-C ports on the back, meant for hooking up other devices and accessories. Stereo speakers, a microphone, and a camera are built in.

The Ultrafine 4K.
The 4K monitor scales back to 21.5 inches, with a top resolution of 4096 by 2304, but retains P3 color. It can connect to a Mac using a lone USB-C or Thunderbolt 3 cable, but only provides 60 watts of charging power versus the 5K Display's 85 watts.
Three downstream USB-C ports are present for accessories and devices, which may be necessary as the only extras built in are stereo speakers.
The Ultrafine 4K Display can be ordered today for $699.95, but will only ship in 5 to 6 weeks. The 5K Display will go on sale in December for $1,299.95.
To grab the lowest prices on Apple's new MacBook Pro with Touch Bar, as well as popular monitors, see AppleInsider's Mac Price Guide.

The UltraFine 5K Display.
The LG UltraFine 5K Display measures 27 inches, and supports resolutions up to 5120 by 2880, as well as the P3 "wide color" gamut. Perhaps almost as important is its use of Thunderbolt 3, which can power both the monitor and a MacBook Pro via a single cable.
Also present though are three USB-C ports on the back, meant for hooking up other devices and accessories. Stereo speakers, a microphone, and a camera are built in.

The Ultrafine 4K.
The 4K monitor scales back to 21.5 inches, with a top resolution of 4096 by 2304, but retains P3 color. It can connect to a Mac using a lone USB-C or Thunderbolt 3 cable, but only provides 60 watts of charging power versus the 5K Display's 85 watts.
Three downstream USB-C ports are present for accessories and devices, which may be necessary as the only extras built in are stereo speakers.
The Ultrafine 4K Display can be ordered today for $699.95, but will only ship in 5 to 6 weeks. The 5K Display will go on sale in December for $1,299.95.
To grab the lowest prices on Apple's new MacBook Pro with Touch Bar, as well as popular monitors, see AppleInsider's Mac Price Guide.

Comments
https://support.apple.com/en-us/HT204592
Edit: But I agree that $1,300 is high, considering (as you mentioned), that you can get a whole computer for not too much more.
The display isn't pricy at all. In fact, both are pretty cheap. The question is whether, at these low prices, the screens are really good. By that, I mean even brightness across the screen without hot spots, etc. Dell has a new one that costs more, but the screen isn't even enough for good graphics or photo work.
Jeez! The prices aren't high. These are separate monitors. Those will always cost more. They won't sell more than a small percentage of the iMacs' sales.
you guys should look at other graphics monitors. They're all more expensive than these, by several hundred bucks. Some by a lot more.
No thanks to this. Lets have a really nice machine and look at an LG logo. Thanks Apple
At this rate I wouldn't be surprised if the Mac Mini disappears from the store and the Mac Pro is removed with a useless page on apple.com showing how you can use an iMac or a MacBook Pro Touch to do the same thing.
They don't care about the Mac, professional, IT or anything like that anymore. That all died in 09
For me, as a professional, the Mac just got better. I can't wait to test out USB-C charging in my vehicle. I already ordered extra cables so I can test via multiple USB-C ports. If you use Adobe I'd think today's demo would be exciting.
I love my 27" LED Cinema Display, excellent quality, beautiful design, nothing else like it on the market.
Too bad Apple has given up on the Mac
(The stickers supplied with all Apple computers and mobile devices are probably too big for that bezel.)