Got bearings replace-now speed sensor broke

So at 150k I decided to replace the front bearing assembly on both sides due to some noise. At the local shop it ran me $640. After it was finished they said, "while we were in there, we found you had a bad speed sensor, and us moving it around was just enough for it to finally go out. We'll replace it for the cost of the part: $150." I don't know how much speed sensors cost, so I don't know if that's even a fair price. Moreover: are they just trying to charge me for something they broke? If so, what power do I really have now to do anything about it but pay the $150 for it to get fixed?