Oxygen sensors

i was wodering if there was anyone out there that could help me i am an automitive student and i am doing a term paper on O2 sensors and i was wondering why you can't use $20 sensors in place of $200 and $200 sensors in place of $400 sensors. any help with this would be great i know it has to do with the material that they are made of but i need more than that knowledge to finish my paper.
thank you :grinyes: