I'm not an attorney but I do know something about common sense and my own morality.

If a seller is willing to offer an item to me at a cheaper price because he is giving me a CHOICE on the insurance... To me that indicates an agreement that he is taking that cost out of the core shipping and handling charges and allowing me chance to pick which way to go on it. (I know - you say it requires specific verbiage to make that a legal binding agreement).

Sure you can hid behind a technically of law but sometimes you have to take responsibility for what you elected to do as a buyer. In my opinion if you take advantage of an opportunity to get something cheaper with that in mind and then you call "foul" later is unethical in my eyes.

That's just my opinion. Maybe you can sleep at night knowing you got something cheaper in this fashion but I would never ask someone to give me a refund if I had the chance to decline insurance and I took him up on it. Especially with a fellow club member.