I don't think I can remember a time when anyone came up with a true estimate of a future aircraft's operating costs. No point in getting too excited about it yet; there is a long way to go and way too many unforseen issues yet to come. With the best will in the world, today's estimates are always based on the current state of the project and/or what the forecastesters hope will convince the people with the purse strings to remain on side.