Even with a coupon or membership to CW RV supplies are cheaper elsewhere. That goes for GS too. And sans all the junk mail overflowing from your mailbox.
There are small camping stores through out the states that carry the same stuff Camping World does at 'half the price'. Most local RV dealership has a small store inside for common camping and RV parts at half the price of Camping World.
I found 'many' GS CG's that manipulate the cost of the price of their per night fees to accommodate the 10% discount. When you check in and ask the rate and then present your membership card and the owner says "Oh the discount is already in the price"? Yup and your checks in the mail. :R