I've found that in our area its always better to be polite and treat everyone kindly as you never know who knows who. I'm only just now beginning to find out which of my customers are friends with other of my customers, and I bet there will be many more revelations in the future.
Be smart/rude with one and you will damage your reputation elsewhere, sometimes with you not knowing it. We are professional window cleaners, not comics. If you can come to some arrangement that helps you both in these tougher economic times, then great. If you can't, then politely 'walk away'.
My personal take on this is to try to keep your customer base if at all possible. Once you walk away and they find someone else that will clean to their new requirements, then you have invited another window cleaner into your 'patch' - so there is also a bigger picture to be looked at as well.
This was especially true in the motor trade. If a customer was happy with your service he would always come back to you. If you upset him, he would go somewhere else and you didn't see him again. The loser was actually the saleman who upset him, not the customer who went somewhere else.