Because its a starlight camera...dont fall for the resolution scam...5mp is NOT 2.5x better than 1080p...you will suffer low light issues....with domes you will have ir reflection issues. Buy a reliable brand with a good sensor...forget the hype. If you get the varifocal model, then the 1080p camera can actually produce a higher pixel per inch depending on the exact level of zoom you use.why its only 2mp ? And 135$ ?
see nayr's review in the dahua section..oh cool you have a link ? I find only cams with manual lens