As a marketer in my day job I am often buy creative services such as graphic design and less frequently, photography, so my perspective comes from the buying side of the transaction.
It would never occur to me to ask for free services and if someone were willing to offer that I would worry about the quality.
However, it is common to negotiate prices and it’s often expected by my employers, especially for a large project. Good creative professionals never act offended or defensive in such a negotiation (assuming I initiate it politely). They might hold to their price with some explanation; they might offer a small discount as a gesture of good will, or they might suggest a way to scale down the project to meet my budget. All are legitimate responses that keep open the possibility of business now and in the future.