Yes, heavy liners are not only expensive to ship, they're difficult to install. Even liners for moderately sized ponds may require heavy equipment and a team of installers. Imagine trying to shift a ¼ ton sheet of unreinforced EPDM a few feet to the left without dragging it!
Unreinforced liners are also prone to tearing under their own weight, but liners manufactured with a reinforcing scrim (like RPE) have a significantly higher strength-to-weight ratio so you can get the same amount of durability from a liner only 1/3 the weight.
