Starbases vs Warships

[wraith]

I'm trying to understand the advantages of starbases vs the a sub-light warship with the same tonnage.

1. A 20,000t sublight warship (CTS Slowvette) costs 150eu.
   
2. It ages and would require 4eu (150/4 rounded up) per turn to keep at Age 1.
   
3. Maintenance is 40eu (20,000/500) per turn. Sublight reduces that to 30 (a 25% discount).
   

1. A 20,000t starbase (BAS Stinger) costs 200eu.
   
2. It would require 5eu (200/4), per turn to keep at Age 1.
   
3. Maintenance is 20eu (20,000/1,000) per turn.
   

The starbase costs 50eu more, but saves 20eu on maintenance costs per turn. (19 eu if we're upgrading each turn.) That would add up pretty quickly.

You can use a CONTINUE order to add to the tonnage of the starbase. Combat is based on the "power" of a warship, which increases at about log(tonnage), so a more massive ship has more combat power than two smaller ships with the same total mass.

Examples might make this clear.

Building two corvettes, total mass 40,000t.
  BUILD CTS Slowvette 01
  BUILD CTS Slowvette 02

  Species    Tech Levels  Num   Offen  Defen  Fleet
  Name       ML  GV  LS   Shps  Power  Power  Maint
  Foobaru     8   7   8      2      0     53     58

Building one starbase, total mass 40,000t.
  BUILD BAS Stinger, 400

  Species    Tech Levels  Num   Offen  Defen  Fleet
  Name       ML  GV  LS   Shps  Power  Power  Maint
  Foobaru     8   6   8      1      0     61     39

[Wilks]

It is my understanding that a starbase can also be added on to as the game progresses and as you can afford it.  You can later make your 40K ton starbase into a 50K ton starbase.  That is a bigger jump in Power compared to adding a picket boat to your 2 corvettes.  One big ship is better than a bunch of smaller ones.