Steve,
I hand made a piece of jewelery for a girl some 25 yrs ago and had it gold plated for $40 back then at an industrial plating biz. I would think under $120 would be 'reasonable' today.

A few yrs ago, I had a Nitro Spcl toplever built up with hardchrome under the crossbolt (it was gold inlaid on the top, otherwise I would have welded it) to tighten the worn crossbolt. The guy built up about .040" but took two setups to do it. $75.