I have had great luck with $1 per minute for the folks who want "just a cut or two." When we get started I look at the shop clock and say "looks like 3:15 to me. Right?" That way, if the boards are in good shape, and the cuts are pre-marked, I can whip through it in no time. But if they are going to stand there and say "2 inches... no 2 1/2 inches.... no make that 2 1/4 inches" the meter is running. For that price they get me and any machine in my shop (they don't touch any machine). If the wood is dirty, I clean as required.... as the meter runs. If you want a fancy invoice, that is part of the time.
I had one customer who wanted a cut on a gun-stock - without taking the barrel off. Took about 40 minutes until he was happy the way it was aligned on my saw, and he paid me $50 with profuse thanks.
I had another customer who had made a frame, and wanted another frame around it... he assured me that the cut was a perfect 45 degrees. I could see that it was not. 1:15 until he figured what angles he really wanted me to cut for each piece, so I charged him $75. He thought it was expensive for cutting 4 pieces. I hope he doesn't come back.