I'm running a cheap (it was about $50) Chinese unit labelled as "HDE-C18" (but I've seen what appears to be the same exact product sold under other names like "i1000").
The picture quality isn't that great (check YouTube for examples). It can read license plates if the other car is close by, but after a car-length or two I start to lose those details. It's much worse at night, when things get really grainy. It will manage to pick up license plates if I'm stopped at a red light, where my headlamps can light the plate up. Maybe some day I'll upgrade to something with better picture, but I'm afraid that's going to be somewhere in the triple digits to get all the features I want.
But aside from the image quality, it's actually very good for the price. The picture is still technically "HD", and it has all the common dash-cam features like loop recording, motion detection, still image capture, etc. Best of all, it's dual-channel so it can record what's happening behind me. I also like that it's low-profile and I can tuck it behind my rear-view mirror instead of having to mount some chunky GoPro unit.