I own an auto repair shop. If I had a dollar for every time some clown tells me that his neighbor will do a job way cheaper, I would retire. It is very satisfying when they call me for help after their neighbor messes up their car and walks away which is a pretty regular occurrence as well.
I may or may not break it down for them.
“That is the total price for the service”
I also remind them that I will not use parts they provide.
“Ok, pay my diagnostic charge and do whatever you want with those (probably wrong) parts you found on the internet”