Talk:Constructing and upgrading costs and time/@comment-212.140.255.180-20110907124640/@comment-3991817-20111022011219

Upgrade to level 1: $ 900,000

Speed up on 25%: $ 1,080,000

Speed up on 50%: $ 1,800,00

Upgrade to level 2: $ 1,300,00

Speed up on 25%: $ 1,560,000

Speed up on 50%: $ 2,600,000

So I guess it is safe to say that in this case the 25% speed increase costs 1,2x the amount to upgrade, and the 50% speed increase costs 2x the amount to upgrade.