[Open-Sourcery]

That price seems about right. Many "CO2" sensors are actually measuring VOC levels then extrapolating what the CO2 level probably is rather than measuring it directly. You can see in the specs that this sensor uses NDIR (Non Dispersive Infrared ) to measure the CO2. NDIR fires an infrared laser at a specific frequency of light which falls into the absorption spectrum of the C-O bond of CO2, this scatters the light; This dispersion is measured and then turned into a PPM measurement of CO2. This sensor says it uses this NDIR technique and so is probably measuring the CO2 directly.