When I say that my wife reminds me that I'm thrifty.
Of course she reminds of a lot of other things.
Some of them do offer flat rate shipping as a special. My personal experience has been with Adams and if you get the shipping reduced there, the costs are more palatable.
The only other suggestion I have is stock up on other things you might need to help ease the shipping costs. I know I've backed out of orders because I couldn't justify the shipping costs for only a few items verse the shipping costs if need a bunch of things and could get a deal the shipping.
Also, double check to see if they do have C5 discount codes. sometimes the discount codes equal the shipping costs.