Title says it all. What'd be the value on this bad boy?

The caverns won't add much to the value cause most will want to cloak it.
As it is say 15K ctp....

But if a friend has it on scan and it can be alerted for invasion, then the artis you have on it can increase the price. Any % cloak artis, and rare +2 arti production ones will too, also +% arti or production ones will increase price.

If you increase the size to VM, use some crystals on it, use a gaia seed on it, use a reality transfuser on it, they will all increase the price, with all those getting you close to, or even over, 50K ctp

Just depends on what you are willing to part with and how much money you're willing to spend.