Yeah, shipping costs do come into play for their profit scheme. I run across this all the time when buying on eBay. With Camping World, I typically just make a list and purchase whenever I'm in a CW store....which isn't too often.
As for Prime. It is $99/yr so you gotta order quite a bit to reach this level in shipping costs.
So far this year I have ordered/received from Amazon a complete tow bar,, base plate, light kit, umbilical cable, emergency break away kit, screen door handle, laser temp gun and many, many other small miscellaneous items. Total shipping for all of these was just over $50.
Will I be ordering more from Amazon this year? You bet, but certainly no big items. You have t order a large amount of things, or very large to reach the $99 mark.
I have, in the past, ordered from Amazon a very large $3000 table saw, $1000 band saw, and a $700 drill press. All were free shipping so Prime wouldn't help at all.
Ron