1 billion is way to low - a Cutter only costs a billion!
So how much larger, more complex, and more materials, goes into a (small) megaship... They should probably be 100 billion minimum, or more realistically 1000 billion+ if you think about how class scaling works: class 9 power plant is 0.5 billion, class 10 is 1.6 billion, class 11 is 5 billion etc.
It will certainly be interesting to see how accessible they are to players.
Not sure megaships count as "end game" though, unless they get gameplay content added which is not accessible to non-squadrons. They'll just be a convince thing and "guild hall".
A cutter costs 1 bil to max out for combat... not in stock price alone... 100 billion for a glorified station that carries only 4 pads at best?
Elite Dangerous's only fault is it's own community and it's half cooked ideas they love.