Not every honest, down-to-earth attempt at pricing transparency turns out well.
The following is a 100% real proposal for illustration services. The grand question for you is, how much money is this about?
I count around 6 hours from the agreement, sketches, and revisions, to the final ink for those things that were in the book; translated into a timeline, it is 2-3 days per image (I include some buffer in this, if we understand each other correctly, it is almost 1-2 per image of course).
I calculate an hour of work as €45, if we work in that style, the calculation above is good. If we do something else, it still stands, but depending on the complexity, I would introduce a cap for a reasonable time, e.g. 50% over, before any changes.
If your immediate answer was 810 EUR, congratulations on being admitted to Hogwarts because you are clearly a clairvoyant witch/wizard.
For the rest of us, that proposal is a good reminder of just how disorienting it can be for clients to hear the raw formula that makes sense inside our heads. And so many of us are guilty of this at times. I’m not an exception, I used to take a whiteboard to meetings because without it I struggled to explain the old pricing model to clients.
Make whatever calculations you need first, and then propose a clear, simple number to the client. Ifs, buts, and maybes belong to the negotiating table, not the proposal.