I can see where you are coming from but the math just doesn't make sense logically... it is true that the tops make up the majority of the order; however, they do not make up the majority of the weight/shipping cost.
If you figure that a top alone is only about 30 pounds.. the bows are about 60 pounds and the doors are about 90 pounds (just guessing)... then the 18 tops in the order make up 34% of the shipping costs, the 13 bows make up 49%, and the 3 sets of doors make up 17%. If the shipping total is $2500 then that comes out to $42.37 per top, $94.34 per set of bows, and $141.51 per set of doors.
So if you bought just a top you would pay 42.37 for shipping.. if you bought a top and bows it would be about $136.71 for shipping.. a total of $811.
Using the same method.. and having shipping cost a total of 4k the total for a top and bows is about $900. ($75.47 for top, $150.94 for bows, $226.41 for doors).
It is still quite a big jump in price comparing sea to air.. but I just wanted to point out that the prices haven't gone up that much since the last shipment. (yes Ehsan has increased has prices and gas prices have increased) but if you calculate shipping by weight then it makes a little more sense.
My point was that if we pay for shipping by air, some folks' cost (those with the heavy s***) may be substantial in actual dollar terms and that we shouldn't be talking about "just an extra 90 bucks" because it's not going to be that way for everyone. I think you made the same point, whether you intended to or not, because under your numbers, bdyer, for instance, is going to pay $174.60 more to ship by air (that is, more than the $278.22 he'd pay to float it).
But since you decreased my cost, I'm now voting for air.

What's the count?