$75 is just nuts.
Their picture indicates the stuff coiled up, and would likely fit in a USPS Large Flat Rate Box for about $20.
They refused to ship anything at all to me in Alaska, even though it weighed less than a pound and would fit in a small box. Got the standard "we don't ship to Alaska"
You might ask them if it can be coiled and shipped normally. I've had stuff shipped to a freight forwarder and paid them to ship it to me and it was way more stuff than an "oversize" shipping tube. I've also bought a 5 ft length of stainless steel tubing and it was shipped to me for way less than $75.
Here's the info (I think) from Chev's of the 40'sWindow Channel Kit With # 4070069 Rubber - Quarter
Item # 4070069C 47^54
This is a window channel kit with quarter window rubber (#4070069). Fits Suburban. Complete for two windows
The 54.3 lbs kind of blows me away, though. Must be the windows as well for that kind of weight, unless the channels and rubber are made out of lead.