Here's a $199 GNU/Linux handheld: http://noodlepi.com. AFAIK it's the world's smallest, lightest and most open handheld computer. Can be assembled / disassembled / upgraded / repaired by end users in under 10 minutes with no tools.

Awesome device, I didn't know about it! Added it to the devices wishlist in the postmarketOS wiki: https://wiki.postmarketos.org/wiki/Device_Wishlist#Mainline_...

Thanks for sharing!