let's say 2,4,8,16,32 so this would range from 18 p/m to 288 p/m ?
Sounds good if you mean: 2,4,8,16,32,64
All together, there are six HQ buildings.
My attention is to have for small and for a well developed networks headquarters with a price level that's gives the player a financial target. In other words the first HQ is cheap and the last one will cost multiple more than any highspeed train. Like in the real world you can start in a barrack ... until you buildup a skyscraper.
biggest HQ: 9 * (64-1) * 2500 ~ 1.417k
That's still less, I compare it with trains:
a four station long "RENFE Class 447" train is more then 1.000k
a four station long "BR-373 Eurostar" train more than 2.213k
a two station long "RVg 0-4-0T" bulk train (year 1901) about 88k
To give small network player a small price, what about:
Result: first 90k, ..., last 11.430k