If the platform weighs 100,000 ton and scrap iron is between $50 and $100/ton, then the rig's scrap value can't be more than $10,000,000, but it can be a lot less. Maybe it costs you a couple million dollars just to have it towed back, then maybe a couple million in labor and tools to cut it up, and a million in hazardous waste (asbestos) disposal, and so on. TBH, I don't know how much all of this really costs, but I can see where dismantling a rig could potentially cost quite a bit more than its scrap value, and thus the thing can have a negative value. In that case it might be quite attractive if the owner of the thing can transfer that responsibility to someone else. They might even pay you to take it.