When I was younger and (if possible) dumber, I took in an old gun promising to make a needed part. I told the customer the gun was not worth the work, but he pleaded that it had sentimental value and he wanted it repaired in memory of his father, boo hoo. When he came in to pick up his gun, I gave him the invoice, which was for several hours labor. He told me to put the paper in a dark place, that the gun wasn't worth that (no more sentimental value BS!), and walked out.
I never made another part for a junker unless I got a big deposit up front.
Jim