Artisan,
that's a bummer and the last call would be one you really need to think about as far as any other income (ya-know paying bills , just the normal everyday living things, etc) you may have coming in.
If it meant that I "really" needed the money to survive getting bills paid, etc. as mentioned above, I probably would go ahead and BITE THE BULLET AND DO JUST THIS ONE.otherwise, I would stick to my grounds and tell the homeowner whose house just sold for $550,000, he probably needs to find someone else to do his work. I mean "come on" here they buy a home for that kind of money and then expect to get everything they want done for less, which would not just be you, it would probably be anyone they deal with.
Now, I have on occasion when I am the same person doing other work at a later time for the same customer, I will give them a discount, but this is only for repeated customers.
I think once you get started on this job, you will find this person may knit-pick at everything you do. geez, just the higher walls is enough to say no, not to mention he will more than likely go out and brag about how he got such and such done for this price from a painter by the name of Artisan, and you may find in the future some of these people may just be people he has spoken to and they might just want a discount from you also.
Lets face it, when it comes to a plummer or someone coming out to do repair work on something for someone- they have their labor charges and by cracky they ain't cheap, and the customer doesn't seem to buck at all, but when it comes to a professional painter - people want to try and nickel/dime you to death and get a quality professional job done for nearly nothing.
So, unless I really really needed the money, I would just hold my ground and say NO.
good luck.