Upfront I do not know if that is a reasonable cost for a high quality job or not. In my profession quality cost more because of the time it takes to do a quality job. So getting an opinion from someone like Bill Thalmann ex conrad johnson could be a prudent inquiry.
I had a amp I thought of repairing and rebuilding/upgrading. I didn't do it. I got a new amp and that seemed to necessitate other changes that cost. So you may figure that in to your situation. Not only did it cost more that just the amp for me to be happy. It took a long time for everything to settle in. If I had to do it over again I would have got it fixed. Just me though.
I had a amp I thought of repairing and rebuilding/upgrading. I didn't do it. I got a new amp and that seemed to necessitate other changes that cost. So you may figure that in to your situation. Not only did it cost more that just the amp for me to be happy. It took a long time for everything to settle in. If I had to do it over again I would have got it fixed. Just me though.