Is it likely that SpaceX will have actual reasonable demand? Their major customer is Starlink. How legitimately confident are we in the numbers with regard to price reduction vs creative accounting to offload costs to Starlink and subsidize the launches to appear to offer huge cost reductions?

If there exists sufficient demand for the product of space launches then it's probably reasonable to expect their to be a near-peer competitor soon, but that's only if SpaceX were to be profitable, which it isn't, even with the subsidization by Starlink on the order of many billions.