I think you're somewhat underestimating the civil costs at the upper end.
It's public domain that Bombardier's CSeries development/launch costs are of the order of $2.5bn (the terms development and launch seem to be being used interchangeably). (See
WSJ as an example, citing $2.5bn)
Using the level 4 costs, it'd be $0.5bn + 4 aircraft at $50m + the same again, or about $900m total. That's under by a factor of about 3.
A while ago,
Boeing took a charge of $2.5bn for the first three 787s, which it said it wouldn't be reselling. Since that was stated to be associated with the test aircraft, it must be a low end bound on their costs - I'd be surprised if the total development/launch cost were less than $5bn, and if you told me $10bn it wouldn't be a shock either.