God. Bosch OEM sensors are $95 amazon prime, shipped to you in two days.

https://www.amazon.com/Bosch-16413-O...008%3Abmw%3Ax5


Ive done O2 sensors driving a car up onto a curb and wiggling under....

Time for a new shop. Heck, even amazon has a "$199 installed" price. 800 for all 4, and there is NO WAY that installer would charge the same for the other 3 once he is there.

DO NOT just change these unless they are diagnoses bad OR they are over 75k on them.