I have usually taken the Strategic Construction Cost for a Campaign as being equal to the Combat Rating of the ship divided by the Tech Level Modifier used in designing that ship. This means that a ship with a high Tech Level will cost more than a ship with a low Tech Level. I think that I decided to use this House Rule as a deterrent against Pocket Battleships.

A ship at a Tech Level high enough that it carries twice as much in Weapons and Defences as a Tech Level 0 ship will have an impressive Combat Rating. However, it will not be at an advantage against a similar Strategic Cost invested in lower Tech Level ships.

If I am engaged in a long Campaign (one where Research, Development, and increase in general Tech Level is important), I set the General Tech Level of a player as being equal to Tech Level 0 for purposes of this calculation. His construction bays would be permitted to construct ships at Levels up to three Levels higher or lower than his general Tech Level. I often label these provisional Tech Levels as Archaic, Primitive, Crude, Standard, Advanced, Cutting-Edge, and Experimental.

Players at a higher general Technical Level would be able to field a fleet at the same Technical Level as their enemies, but at less expense per ship. This is likely a better way to win a long Campaign than trying to produce a small quantity of high tech but very expensive ships. It also encourages spending more of one's Strategic Income on raising one's general Tech Level than on researching more powerful weapons with exotic Traits like Catastrophic Damage.

I should probably mention that I use the Starmada variant of the Victory by Any Means Campaign System when I am playing Campaigns. I find that this is a very flexible and easy to adapt set of rules. It was well worth the money that I spent on purchasing the books.