I have check engine light on, Error code P203B00. Am told needs an Add Blue Pump

What is your question?

Am told the Add Blue Pump costs $700 plus labor. The check engine light does not light every time I start the engine. I have only 46,000 miles on the car and am told the part is not covered under warranty. Seems like something like that should be covered or not so expensive. Is this part of the emissions and is it crucial to be replaced? Would the EGR system have anything to do with the error code P203B00?