Hello hugh2711, I'm a bit late with replying but I have info. There is information scattered about, but a recent post by the lead developer has given some extra insight.
OK, you already know the softcap is meant to gradually lower your income as your fielded units start to get more expensive. SE units are excluded, so this means their cost is not used to limit your income. Auxiliary units & reserve are excluded as well, only the core units that are one the map are used for the calculation.
Every scenario, you are allowed to deploy a certain number of units: these are your core slots. Let's say you are allowed to field 20 units. If these 20 units have an average cost of more than 400 prestige (pr) than the game will start lowering any prestige income (from capturing objectives, scenario bonuses, etc.) by a certain amount. Normally you would get 100pr for a Victory Hex (VH), but if your fielded units have an average cost of more than 400pr you will receive less. This lowering cannot go lower than 20%, so you will always receive 20% of the normal income regardless of how expensive your units are.
Each time you receive prestige, the game calculates the exact cost of the core units on the map, and adjusts the prestige. So if you lose units during a scenario the average cost of all your units will change, and so will your income. So it is important to realize what this average cost is and what counts towards it.
Unit cost/core slots
what you pay for a new unit is the baseline cost. An Elefant costs 600pr, well above the 400pr mark. So if you have 20 core slots and field only Elefants, average unit cost is 600pr: ((20 x 600)=12000)/20= 600.
Way above the 400pr mark and you will see your income lowered considerably.
But if you have 20 core slots and field an army of just 13 Elefants and nothing else (or SE units), the average unit cost will be ((13 x 600)= 7800)/20 = 390pr. So your income would not be lowered, but you'd have less units deployed.
Current strength
When units take losses they lose strength points. This is taken into account. A 10-str Elefant is 600pr, so an 8-str is worth 480pr. a 3-str = 180pr. If you have a lot of badly damaged units you will see your income increasing as you play.
Overstrength
Overstrengthing a unit makes it more expensive, so it counts towards the softcap. Let's take another Elefant.
At 10-str, it costs 600pr. Suppose it is a 5-star unit, and you purchase all 5 steps of overstrength, making it 15-str. You might think each step is worth 60pr, but just like when you purchase overstrength each extra step of overstrength is progressively more expensive. The game calculates the value of each point of overstrength like this:
First point (11-str): 100% of 60pr, then multiplied by 2: (1x60)x2=120.
Total value of an 11-str Elefant: 600+120 = 720pr
Second point (12-str): 150% of 60pr, then multiplied by 2: (1.5x60)x2=180.
Total value of an 12-str Elefant: 600+120+180 = 900pr
Third point (13-str): 200% of 60pr, then multiplied by 2: (2x60)x2=240.
Total value of an 13-str Elefant: 600+120+180+240 = 1140pr
Fourth point (14-str): 250% of 60pr, then multiplied by 2: (2.5x60)x2=300.
Total value of an 13-str Elefant: 600+120+180+240+300 = 1440pr
Fifth point (15-str): 300% of 60pr, then multiplied by 2: (3x60)x2=360.
Total value of an 13-str Elefant: 600+120+180+240+300+360 = 1800pr
So this adds up really quickly...
Than there is another important factor to consider:
Cost of transports
If a unit has an organic transport (truck, halftrack) this cost is added to the value of the unit, and when overstrengthing the same cost mulitplier applies for both the parent unit and its transport. So those 200pr halftracks will drive up the average unit cost a lot. A couple of examples:
'43 Grenadier (227pr) + Opel Blitz (50pr) at 11-str: 332pr total value.
'43 Grenadier (227pr) + SdKfz 251 (100pr) at 11-str: 392pr total value.
'43 Grenadier (227pr) + SdKfz 250 (200pr) at 11-str: 512pr total value.
Here's an interesting comparison: both these guns have a rate of fire of 80%, so for an extra shot you need them at 12-str, 11 is just a waste of prestige:
15cm sFH (271pr) + SdKfz 251 (100pr) at 12-str: 556pr
17cm K18 (310pr) + SdKfz 7 (70pr) at 12-str: 570pr
So the heavier gun is actually pretty cheap if you want a halftrack as transport. For this reason I use either sFH's with trucks or K18's.
As for the exact income penalty, I had long assumed that this would be linear, and that there was a bug in the calculation as the values I observed did not seem to match my calculations. What was certain is that the softcap seemed to hit that 20% minimum at around 625pr average unit cost. Well, I was wrong, it isn't linear... Here I've pasted the math for the softcap as given by Rudankort:
Rudankort wrote:There are several values governing the work of soft cap. First, we have Normal Prestige and Max Prestige, per unit slot in the core. As these names imply:
- To have Normal Prestige amount of prestige is, well, perfectly normal, so no adjustment of income is necessary. The player gets full income from whatever action he performs.
- Max Prestige is, well, the maximum amount the player is allowed to have. So, once the player reaches this amount, he must be getting zero.
This means that between Normal Prestige and Max Prestige player's income must gradually change from 100% to 0%. How exactly? Well, various approaches are possible, but the game uses parabolic function. In other words, between normal and max values of prestige, the following coefficient is applied to income:
(MaxPrestige - ActualPrestige)^2 / (MaxPrestige - NormalPrestige)^2
This is the basic mechanic. But if player's income ever dropping to zero sounds too severe, there is an additional parameter in place, called MinKoff. If it is not zero, income coefficient is never allowed to drop below this value.
The bottom line is, there is no bug in soft cap implementation, but there has been a misunderstanding how exactly this feature works.
If current values set in gamerules are too severe and break balance in some scenarios, this might be a balance issue which needs fixing, but a fix would be related to adjusting values in gamerules, not in the algorithm itself. My approach to this has been as follows. 800 is a lot of prestige per unit (somewhere between Tiger I and Tiger II cost), so getting to this value should take a lot of time. On the other hand, half of this value (400), which is about average unit cost, should be easy to have.