1-2 lbs makes a big difference when spinning at 5,000 rpms. It also has an impact on the driveshafts critical speed. Determining "worth" is always subjective. What is "worth" it to one person might not be to another. My car has a harmonics issue at high speeds in the drive line. A carbon fiber driveshaft would be "worth" it to me. Less rotational mass, stronger, better dampening, safer....so what's "worth" it to you?