I only have the 1 vehicle and know the original mobile estimate was over $300...there were multiple electrical system error messages so I think they included those, but everything cleared up once the battery was replaced.Not for replacing a 12V in a model 3 its not. It might be that much in a model S or X though. Are you perhaps mixing the cost up with another vehicle you own or used to own?
My 2nd estimate was $117, but they did it under warranty as I was below 40 K and had asked about other potential issues while within 4 years of purchase.
Mobile service was quick and convenient!