[Bobcat]

One possible answer is that they are set up to make new product on an assembly line . To rebuild a shock , it must first be taken completely taken down (labor here ) and all parts inspected and the ones that need it replaced , shock reassembled and tested . Again , time to do this vs an assembly line . They are also doing this on a much smaller scale than manufacturing .
One of my company`s Divisions made hydraulic cylinders ... to repair one cost almost as much as a new one for the above reasons . We also had to base our pricing on a worst case scenario .
Don`t know for sure , but I suspect that may be why a repaired one approaches a new shock cost .