From the information I've come across, litecoin source contains SHA256 algorithms, only the memory requirement is more.
Why not add massive 500GB of non ECC memory to a server board and some bitcoin mining chips?
Am I missing something or is 3TH of scrypt hashing power on ltc just not worth the effort to any dev out there?
The essence of what you wrote is true: Scrypt does require a massive amount of memory to be hashed, however, this cannot be added to current BTC ASIC equipment because Scrypt is using a modified version of the SHA-256 algorithm, and since the ASIC is specific to the SHA-256 algorithm, it won't be able to work with the modified version, AKA, Scrypt.
Atleast, to my understanding.