I have to agree with Junkie. I have left a mess in the past, at the customer's request, and what would take me two hours will take them all weekend. After they get done paying dump fees and figure how much time they've required of their friends helping, they've done everyone a disservice, including themselves.
Now, when I see this coming, I negotiate for them, on their behalf. It might go like this, "I can certainly appreciate you wanting to save a few bucks, but I've seen a few people get in over their heads. All I want to do is provide you world-class service, so how does this sound? Let me get rid of all the brush, and I'll cut up all the big wood into regular firewood chunks. Then I'm gone. Your job will be to move the firewood and stack it, and rake up what's left. For this I'll knock X% off the quote. This will save you X dollars and it won't cost you your weekend."
This is a win/win. All she wants to do is get 'a deal' and feel like she has some control over the bargaining. Our job is to make her look like a hero, and let her know you're reasonable, and that you care. This will get you the job, and get you referred on.