TL;DR: Steam briefly showed options to buy refurbished Steam Decks for the following prices:
- 64gb - $319
- 256gb - $419
- 512gb - $519
The steam page has since been taken down, but will hopefully go live officially soon.
Edit: That was quick, refurbished units available now.
They have to say not to open so that they aren’t liable for people breaking it when opening it. Some aspects of the hardware are hard to work with, like replacing the battery, but joysticks and screens (the main things I would expect people to need to repair) are surprisingly easy to access for a modern portable device.