“So why is it 20 GP if all you did was wave your hands around and chant some incantations? Anyone could have done that…”

“Here’s an itemized bill. 1 copper piece for waving my hands around. 1 copper piece for the incantation. 1 copper piece for the scroll... 97cp, 9sp, and 19gp for the education and experience to know which hand waving, incantations, and spell scrolls to use.”

Seriously, every single freelancer or contractor has gotten the “Well I could have done that, what the hell am I paying you for? That only took you like 10 minutes” response after their education and experience makes the job look easy.