The cost of the OneWire systems fundamentally come down to the interests or willingness of the individual to do electronics. If someone has some reasonable skills then it can be very inexpensive, and unique sensors can be built. Buying the OneWire modules that plug together is about 10X the cost. For those that make their own some with understanding of reliability can yield a pretty solid network – for example mine provides the data to control my pool depth and temperature, and gives me very sensitive temperature analysis for a molecular film pool cover performance.