I just bought a Lenovo Ideapad U310.
"Ultrabook", though looks more like a MBP than a MBA, 13.3" screen, i5 3rd gen, 4GB RAM, and 500 GB HDD with 32GB SSD.
All that, used, for 470 USD (expedited shipping included).
After purchasing it, I figured, since it looks very much like a MBP on the inside, would be awesome if it ran OSX. So I Googled "U310 hackintosh" and apparently it's do-able, all its insides are used by real MacBooks so it works pretty well, so I'll certainly try it.
Also, it's got the best keyboard on an Ultrabook, trackpad too (MBA isn't an Ultrabook because it's not a PC, obviously the Macs have the best trackpads.