There are big favors, and then there are big favors. I would equate Isabel’s request to asking a friend to drive you to the airport 50 miles away at 4:00 AM in order to save the cab fare and parking fees.
On a completely unrelated note, Paul and I really appreciate everyone who leaves a comment. They’re like fat free donuts that actually taste good. They help energize us to keep doing what we’re doing and we can’t get enough of them. So keep those comments coming.