Hi WGT,
Personally I think it is a bit high... but does depend on the amount of "altering pipes" that is needed.
I would recommend getting a few quotations for this work, but remember, the cheapest might not always be the best. If you have friends / family that have gotten plumbing work done, then look for a recommendation. I would look for at least 3 quotations for such a job... If you can give your area, maybe members on AAM could recommend someone that you could get a quote from?