I'm in the same state as you, drafting a commission sheet for the first time in my life.
I also feel uncomfortable with the hourly rate and agree that perceiving originality it's in the eyes of who's looking.
So how about focusing in the different parts of the proccess that brought you to those finished artworks you showed?
This is my draft, I put the sketch as the main part (since it's something I have to do no matter what they ask me for) and further steps, that are all choosable, are a smaller amount to add to the first one.
I show you the sample sketch, after that I may include different little versions of the maths up-there to them to check on the different possible results
It seems like I'm self-promoting but I really came here yesterday willing to ask the same questions as you and I've been following this thread closely since then
Back to the point, rating the price of an artwork as a whole finished piece may work if you're going to sell it. But if you're going to accept commissions, it may work better to show the parts of the process you go through, so people know where they are putting their money and you know what are they paying for