Small Scale Military Headquarters

I have a few 1/18 in box planes I may want to sell here. For those who ship a lot, what is the most economical and practical shipper to use?

I've seen shipping costs go through the roof lately. From here in Ohio to the Pacific Northwest is often more than double that from say, Missouri or even Wisconsin. An army helmet from Illinois was calculated at $7.65 on SGoodWill.com. An identical one from Hillsboro, Oregon was calculated at $19! I got the one from Illinois with shipping for less than just the Oregon shipping. Some shippers, inconsistantly by the way, charge extra for "oversized" packages. Found this out on Shopgoodwill.com where a 1/18 plane was calculated at 45 lbs. due to the size. I bid on a 1/6 jeep that shipping would have been 18.95. Another of similar distance was $48 because of being "oversized". Both were UPS.
If I see an item on there and find out it is from Washington State, Oregon or California I usually don't bother because the shipping is outrageous.

Any tips on best ways to go?

I find the US Postal Service is usually the cheapest.

But even they are doing the over sized now.

It seems to me that shipping is starting to go through the roof no matter which carrier that you use.

Axis,
If you compare USPS and say UPS - on shipping planes. They both follow the same zone pricing guide up to a certain poundage. UPS become much more expensive.
I know you can't do this with boxed 1/18 planes, but shipping from Midwest to West coast -cheapest is flat rate boxes by USPS.

I have found the easiest and least expensive way to ship a 1/18 boxed plane is by using 2 copier boxes. Cut down the side of one end of each copier box. Slide one open end inside the other open end of the box. You need packing tape with the strapping strings for strength. I cut the lids of each box the fit on top of one another and tape them up .
Then just tape up your seams (along the middle, bottom and top) and tape along the edge. The box fits a regular 1/18 boxed sized plane.
Razor

I used USPS Parcel Post/Select it was always cheaper to send large items especially to/from Hawaii. It just took longer to get it.