[quote=@TheUnknowable]
Do you have a formula for ship cost, or are you just going to estimate the values in your head?
[/quote]I do and also don't.
A strict formula lacks polish and overall unnecessary for a free play-by-post RPG.
Unlike with tactical simulators, tabletop games and such there's no set value for ships because it's subjective of your writing.
I do have a rough formula to compare the power of ships, though.
Generally I evaluate ships based on how well they perform against others. "How many average ships it can beat alone?"
That's the first viewpoint.
Then I consider other factors like what kind of roles it fills and how well it performs in them.
Lastly I look over the entire ship list and see if this ship has a notable synergy with other types.
Like having a bunch of unarmored ships and a "shield ship" which gives them proper protection.
It'd mean I'd make the shield ships more expensive.

I do have experience with this so it won't be too hard on me.
Still, I could make errors. You're free to argue if your ship is evaluated too expensive, although it'd most likely end with a compromise where you nerf your ship for it to cost less.
Also if a ship type turns out to be much more effective than I originally thought then I could revise its cost for the next battle.
Don't worry, it'll only happen in the most extreme situations.