mine was about £15, it was made in china, you get what you pay for, i figured as long as you can see number plates then its ok, the picture is fine but you can get wider angle lenses, go for the widest.
however some dash cams also incorporate a gps removing all doubt as to where an accident happened, assuming this is why you want one
i brought mine as a back-up for the - it was your fault scenarios, though i have since removed it to make room for the sat-nav, you can get cams that hide behind the rear view mirror. you also need to factor in the cost of an sd card, no point in going any smaller than 8gb, this is used up in about 2 hours. depending on definition. my cheapo couldnt handle more that 16gb, most will simply wright over earlier footage automatically and sense an impact and lock that part of the recording to protecting it. .