$6? more like $60 coming to a scalper near you.
Right now there is stock on a number of reseller sites, and though they might sell through for the first few weeks as enthusiasts bundle up a bunch of orders, I would bet it will be easy to get them at MSRP (maybe with expensive shipping of course) in the next few months at the latest.
The Pico was sold out for a month or two initially, but there's a ton of stock right now—heck, you can buy the RP2040 by the thousands on reels from any distributor.
Though they still had 4k+ units of the non-wifi version (Pico Pi)
They're a lot more plentiful than the mainstream Pi boards.
I think that's reasonable cost-wise for my purposes (I'm making a status display to go inside my white-build gaming 'rig' to look shiny). Red takes about 12 seconds to refresh, AFAICT I should be able to get sub-1s black updates. You can get 7-color versions for about the same price but the refresh on those is very slow.
As ever it depends what you want to do - If you want a 2-inch tri-color display, in a format where you can attach SPI wires easily, you might get away with $20 AUD. You can find small greyscale eink displays very cheap (sub-$1) like this - https://www.aliexpress.com/item/1005003555154992.html
But you'll need to find some sort of interface from the ribbon cable to whatever wires you need.
If you want full-color, fast-update e-ink/epaper, that's just filtering into the market AFAICT, and it's much more pricey. I can find a 31.5 inch full-color epaper display for about $2200(US)!
(There's a video of it in action here - https://www.youtube.com/watch?v=bPnJh4QcjDY)