Newegg offers the Kensington KeyCover Hard Shell Bluetooth Keyboard Case for iPad Air, model no. K97007US, for $16.99. Coupon code "EMCATAN82" cuts it to $9.99. With free shipping, that's tied with our mention from three weeks ago and the lowest total price we've seen. (It's also a current low by $9, although most retailers charge $54 or more.) It features a QuickRelease corner, magnetic well for landscape or portrait viewing, auto-wake and sleep functionality, and scissor keys.
Update: Better yet, buy two for $10.98 via the above coupon. With free shipping, that's $5.49 per case.