Contracting my cost is the difference in costs for a contract across companies versus a purely internal project. This could involve the lawyers on both sides, the time taken to negotiate which party is responsible for what deliverable / risk, the cost to enforce the contract, the time taken for negotiations/ iterations, etc.
One efficient company doing it internally is obviously efficient. Two inefficient companies negotiating a contract is obviously inefficient. The interesting questions are the other 2 quadrants, where the answer may change between the LLM case and non-LLM case.