That's a complex question, so I will do my best to answer using the numbers I have to date.
In the case where the government first leases the ships and later decides to purchase them, the sooner it purchases them, the better it is cost-wise, of course.
I think you're asking me the point at which the price would be more or less equal to the purchase price, $633 million. You suggested that it would be after about 15 years. That seems to be the right point for the purchase of the Asterix and Obelix, especially considering that the fixed rate is estimated to be $40 million annually if the contract is extended, which is highly likely. Under the lease contract, the government basically has to pay $100 million a year. If the government decides to extend the lease contract, it will have to pay the contractor, Davie, fixed payments of $40 million. In short, the 15- or 16-year period you mentioned is more or less on the money, by my calculations.
Given that the joint support ships are much more expensive, I think it would be even longer than 40 years before they became cost-effective, so to speak.
That means the cost difference is substantial. I will no doubt come under fire for saying that since the two types of ships clearly have different capabilities. They are not identical, and I fully recognize that. We are, however, talking dollars and cents, as well as costs. Naturally, the different capabilities or features of the two types of ships account for the cost differences.