Well, this shows you have more common sense than a lot of others out there. I've heard too many times of contract pilots/hobby CFIs who don't need the money say, "shoot, I'll just go fly/instruct for fun. They don't need to pay me."
Oh hell no.
I don't technically need the money but I'd never do that to the local market or the kids trying to put food on their table.
Plus it cheapens the whole thing mentally for the student too. There's a certain seriousness about things that gets lost if the instructor is giving it away for free.
I can see where barter could come into play, but free? No way.
I know what getting the ratings did to my savings account. Thinking about a young guy or gal trying to build time paying that much without any other income, just gives me the willies for them.
Now that said, I've run into instructors who've given a discount when the flying mission or aircraft was a ton of fun... some of the older aerobatics and glider instructors around here do that, or shall we say they, "forget" to bill a few hours of flight time but the expectation is still there of paying their full rate, and then the "accounting mistakes" are made if the flying was an absolute blast. Ha.
I also think my initial CFI "forgot" an awful lot of ground school time, but in the middle of my initial Private he was diagnosed with (thankfully an easily curable form of) cancer, and being a student back then with a bejillion part time jobs, I'd show up at his HOUSE (he offered...) to sit and talk airplanes and frankly, I think it helped him keep his mind off of the damn cancer and chemo treatments when he felt like utter crap.
So besides formal ground school classes at the college back then, I was also sitting around drinking a soda or coffee at his place, digging through a bookshelf full of aviation materials, and asking "dumb questions" the whole time.
He got the benefit of being distracted from the treatment and illness, and I got the benefit of just being totally immersed in aviation stuff for hours on end.
But no. Commercial work or instruction is a job, no matter how fun it is, and saying one will do it for free, messes with a whole bunch of things mentally and emotionally that shouldn't be messed with, and hurts other pilots trying to make a living. Won't do it.