Yes- for a professional welder to come to your house, $70 sounds about right. It's a fair chunk of change, but that's what it is.
I cost me about $100 for a fellow to weld a receiver on my bucket, when I had removed the bucket and taken everything to him. Already had the paint ground off and had made a pattern for the web piece (above receiver) out of thin plywood. On the other hand, I know he did a much better job than I could have!
Of course, you could take a welding course and get a welder.... That would set you back around a grand, perhaps less. If you plan to do a lot, it might make sense.