As others have said, the crap resolution is to mask the crap repeatability. Better processing can help, but good enough processing fits in the cheapest of microcontrollers. ADC quality is more important, signal conditioning and sensor quality more important still. The biggest factor for accuracy is likely calibration though. A sensor that's 2% accurate with a 2 point calibration can easily become a 0.25% sensor with a 5 point, 3 temperature calibration. But that all takes time, and unless you're running huge batches it adds too much to the bottom line of a low cost product. Source: Designed strain gauge sensors and manufacturing processes for a living