idk what you guys have so much of a problem with. $18 is NOT much for shipping on a rather bulky item. i ship snowmobile motors COMPLETE with clutch, secondary, exhaust, intake, wiring, oil can, coolant system, and handlebars for less than $120 and i don't even get a discount or anything.
if you don't want to pay for a box, don't. go to a small local retail store that ships via ups and ask for a box. they'll give it to you. if it has the right length or height dimensions but is too wide, you cut out the middle portion of it, put the item in with newspaper packing, put the ends together (one slid over the other), and tape the sucker up. a roll of shipping tape is 2 bucks, box is free, buyer pays shipping.
If I can send a set of xj bucket seats complete in one box (bottoms removed, headrest removed, folded seats, and put the bottoms and headrest in the box), and their brackets in the other box, all for less than $80, you can SURELY ship the cover for $11 or $12.
(p.s. I shipped the a-pillar trim and a bunch of smaller trim piecs for a comanche in a 4"x27"x37" box for $10.13.)