Seems like a hundred bucks minimum is reasonable for that job.
What do people charge as minimum fee if they are not already set up at a neighbor's house, if any?
One hundred per $5 minutes sounds like a lot of money, until you figure: what if there is a rot column in the tree and it goes wrong and you damage something, do you than try to charge them more for damaging their things to make up part of the cost. Avoiding damage is part of the experience that they pay for, not just your time. They are paying for your liability insures, business license, bond.
They are paying for your drive time, vehicle expenses including insurance. If you pocket $50 bucks and accidentally bump someone's car, professional touch-up will be at least $100 (the saw compartment door on my truck didn't latch right and it swung into the customers bumper at 5-10 mph, putting a tiny scratch, she would not have even know, but I told her--$120 bucks). You could be in a real accident as well.
When you think about possibly hitting a piece of metal embedded in the tree, dulling or ruining a chain, there's expense there.
There is the chance of getting more work from them, but you just removed one of the work pieces, unlike a quick 5 minute prune. There isn't much time onsite for the neighbors to see you, and as well, a simple,no target, felling isn't going to impress the neighbors so much. It is an opportunity to discuss other things that you see in the HO's yard, though.