my car was diagnosed as speed sensor for transmission. How costly is that? on 2006 Mercedes-Benz E350

My car sill randomly loose pressure at 40 mph. The engine light comes on but a day or overnight the speed returns to normal this has been happening for about a month. Is that the symptom? and how costly is that to repair

Asked by for the 2006 Mercedes-Benz E350
speed sensors are approx 200.00 installed but you r have a mbz so call dealer for pricing
the dealer recommends a valve body is this an alternative it is also a more expensive quote
yes but there not guessing