You're absolutely right Dale, there's a lot of factors that determine "Shipping Costs", I bought a passenger side front window for my '59 Fleetwood, the cost of the glass itself wasn't bad, but the shipping costs amounted to almost triple what the cost of the glass was.
When you add up, insurance, weight, packing (the more fragile the item, the higher the packing cost)......and the type of shipping, ie: Expedited Door To Door Air Freight, etc, it can get expensive. But as you rightly point out, sometimes there's no other choice !