iTech Deals via eBay offers its iTD Gear Wall Outlet Coverplate with LED Night Lights in White for $2.89 with free shipping. That's tied with our October mention as the lowest price we've seen for a single plate. (For further comparison, we saw a 10-pack for $24 in July.) It turns on and off automatically via a light sensor.
The dollar store is the most amazing place to find bargains for certain purchases. Yes, even pregnancy tests.