"“Is it a good idea to invest in a locked ely norris cannonball safe?”"
Things to watch for when purchasing a locked canon ball safe; First, the big question is the door free from the body. Most doors that sit unused will be fused shut. It’s quite a job to free the door. Second, are all the parts intact? You won’t know till its open. Most time locks are raped from used safe and vaults. Try finding or machining parts to complete the lock mechanism can be difficult and costly.
"“will it be easy and fairly priced to open?”"
Easy, No. I get a pretty penny to open any cannon ball safe.
"“will the safe be worth anything after opening?”"
The safe can be opened w/o damaged if done by a professional. Unless you can accomplish some of these items yourself, (Moving, Opening, Repair, and Refinishing) it would not be a good investment for your return.
DH