I have a four-string dulcimer to which I'd like to add (or more accurately, have added) a 1.5 fret.
I recall that some vendors at the only dulcimer festival I've been to (in Evart, Michigan) were adding frets for $15. So I thought, oh, great, this will be cheap.
Then I paid a visit to a local stringed instrument shop. First, I showed the guy my three-string dulcimer and asked him to fix a tinny noise I hear on the low notes. He pointed out that the 1.5 fret appeared to be an after-market job. The cut into the wood was not as smooth as it should be, and the fret had started to float up. He put the fret back down but said if it caused a problem again, he would have to ... oh great. Now I forget the verb. Bake it? Sand it? Whatever, I think it involves sanding down each of the frets. Total cost is about $200.
I show him the four-string dulcimer and asked about putting a 1.5 on there. He said it would be about $100 but could go to $200.
So .. .what's the price range for installing a fret? On the one hand, it looks like the after-market fret job (performed when and where I don't know) was substandard, and the guy talked about how hard it is to do things correctly. He said he should measure the place to 0.001 of an inch. Maybe it's gilding the lily?
I know that musical instruments can be expensive, but my (late) mother paid $300 for this four-string unit last year, and I didn't feel like paying $150 or so for a single fret, so I left.