Of course they won't combine your orders, it wouldn't surprise me if there is a bit of profit margin plan on the shipping costs.
After all, most retailers take an average shipping cost and bump that up to cover their dead net from coast to coast. They average out taking a decent chunk of margin from it.
We don't combine or modify orders because it is a logistical problem with the large volume of orders during this weekend. Many other major online retailers have the same policy. Not only is it a logistical problem to unpack and repack orders with so many going through fulfillment, it can mean lost purchases for the customer if the inventory is freed up in the process. I assure you we did not institute this policy to make an extra profit.