Crocodiles are easy. They try to kill and eat you. People are harder. Sometimes they pretend to be your friend first.
When a person who normally charges $100 for their services gives you a pro-bono session, what you are getting is a service that is more expensive than their going rate.
It’s not because they are losing out on $100. Money can be supplemented.
What they are losing is time. Time they could spend on their work. On higher paying clients. Time having sex. Or sleeping. Or eating a really delicious meal somewhere.
Anything else but doing something for you, for nothing.
If you cannot see the real cost of someone doing a favor for you, it’s probably cheaper to pay them the $100.00.
(On the flip side, if you are constantly giving away services you normally charge for, you might want to reconsider what you value.)
Also, remember you get what you pay for. Even if someone agrees to work for free, or give you a discount, or do you a favor it is highly unlikely you’ll get the same quality of work than if you’d paid for it. As David Ogilvy said “Pay peanuts, get monkeys”.