@zukko I'm not aware of a way to do that, but I'm not an expert. The way I did it, you would need to change every unit individually but you can change it by adding a fudge factor.
For example if a t3 unit is normally 400 mass and you want to make it 20% more expensive, you can edit it to say "400 * 1.2"
You don't have to calculate it out and write "480"
This makes it easier to apply the factor or to change the factor. You can use find*replace to replace all "*1.2" with "*1.3" to quickly change the factor used for the mod.
Also from experience, you can have 1 text file that is used to update any number of BP (blueprint) files.
I made a (really bad) mod that does something like that, called ArtiMod