For the most part, the declared value is for insurance purposes I would think, so that if anything happens with your delivery, there is an associated value. Aside from that, differentiating the cost levels ensure that a 52 Topps Mantle is handled differently than a 83 Topps Wade Boggs, which I also agree with.

That being said, I would think of the value more as what you would believe you would be "out" if something were to happen with the card. Since the range is given, look for whatever the high end of the lower range is if you think your card fits into that category as well. ie) if a card is worth $550 in your estimation, there might be a $100-$499 range to look at.

Cheers.