DO NOT OPEN IT! As soon as you open it the platters will collect dust particles and it could ruin any chances of data recovery. Just send it to a data recovery company like Gillware for recovery. Any reputable recovery company will evaluate it for free and let you agree to charges only after...
It could just be a legacy type deal. It's not something that people commonly need so they can charge more for it. RAMBUS memory is insanely expensive for the same reason.
If there was anything important on it I would suggest against the freezer trick. The freezer trick will create condensation on the platters, regardless of how well sealed it is when it's put into the freezer.
If there's any important data on it that you need I suggest an affordable data...