This is like in all other levels. You have cheap and expensive mines.
While the amount of ore, a mine produces follows a constant exponential function like described in the wiki (
https://www.warzone.com/wiki/Mines), cost is a little bit different.
There are mines, which are cheap and ones, which are expensive. The cost for the next level seems to be random up to level 4. From upgrade to level 5 up to level 20, the next level costs always approx 1.8 times more.
If you do mine-upgrades, based on a calculation, which mine gives you most revenue per cost, you will end up with some weird level jumps over your mine list. Unfortunately I just finished Scandinavia without saving my results, as I clean my excel-sheet for each game. One game, where I have a history is Orbis Veteribus Notus, here my mine levels where at game end like the following list. At this time I had the 30% additional ore up to chromium, and 50% only for copper, tin and iron as advancement.
Gaspo 14
Hopesonen 12
Freadwels 14
Valinia 10
Keleginary 10
Proftor 9
Handow 10
Censborogeol 9
Foremotions 11
Andorcel 9
Fectly 10
Ciliked 9
Stramentension 9
Bragpose 8
Probnonders 9
Suffergizes 9
Sparterchacks 10
Judingsions 7
Gicabbonies 9
Rivulstenpers 8
Draugerhytics 7
Shadambuzzler 9
Exienested 10
Echnufitores 5
Flautify 8
Grincurvinding 7
Rowskiman 6
Herobbing 7
Mufficatormes 6
Diserbalned 6
Ottonood 9
Arraight 6
Sketeematic 4
Neutinoclar 5
Bewillo 4
Explum 4
Catated 4
Facipaz 4
Bruther 5
Wagorget 6
Beconch 4
Runnett 4
Farbors 4
Throomize 4
Apiesters 4
Ounded 4
Chase-on 4
Chase-off 3
Purson 4
Fondord 4
Pirelapports 4
Gallinstent 4
Naldors 1
Randix 3
Defegustical 4
Oppingeast 4
Norsents 2
Janeroces 3
Tronnegated 3
Spikeover 2
Paciantry 3
Sponiansumble 1
Toportienative 2
Contairily 1
Ganishare 1
In this list you see for example, that Exienested was a really cheap mine, which I upgraded up to level 10, while
Echnufitores as the next in list was only upgraded up to level 5. Later on Naldors was a very expensive mine, which got not upgraded till end of the game.
Edited 1/2/2022 18:51:08