I agree 100%. In process of buying new one now, and it's totally stupid. Al is lighter. Fglass are in the 150 lb range I'm guessing.
Just found this:
https://www.4are.com/product/mx/dealers/specifications.php
When I had my Tacoma I put on 2 different toppers. 6' bed, cab-high and high-rise both. In both cases, two adult males could lift the topper up and put it into place. I had the same experience with my last pickup, a 1996 Mazda B2300 (a/k/a Ford Ranger.)
But it wasn't much fun and certainly not something I would do on a regular basis. For a full size truck I would imagine the weight would increase by at least a third. 200lbs is more like it, would be my guess.
I find myself going back and forth on the whole aluminum vs fiberglass topper choice. Fiberglass is stronger, looks better, and is better insulated. Aluminum is lighter, easier to remove and considerably less expensive.
As I've said before, it would be interesting if someone cold come up with a modular frame that could have side and top pieces attach to turn it into a hard truck cap. One person could install that in his driveway in a few hours.
I'm sure someone could do it but then the problem is that a quality product would likely be quite expensive.
I guess like many things, you can have it good or you can have it cheap but not both.