I understand your logic of that, but if you don't have a base price to go off of, your only hurting yourself, what is your time worth? For me if i set a price ( even if it ended up being harder) i don't change my price. Mechanics work off a book time, ( I used to do that also) If the book time says 3 hours to change a part, that's what you charged, now if your skills let you finish in a hour and a half, should you be paid less for being better at your job? Set prices help for a base, if the job was easier, say you would give them a " percentage off" which makes them happy and still makes you money. I believe in always helping others the best I can, doing the job the best to my knowledge, but also reminding myself why I'm doing this job, right? Because for me, paying for all the licenses required, insurance, advertising, logos, shirts , all the materials to make a business run PLUS making a salary isn't cheap, lol