- basic transport belt: 1.5 iron-plates
- fast transport belt: 11.5 iron-plates
- express transport belt: 21.5 iron-plates, 2 lubricant
- basic underground belt: 17.5 iron-plates → 2.9 iron-plates/tile
- fast underground belt: 57.5 iron-plates → 9.6 iron-plates/tile
- express underground belt: 137 iron-plates, 4 lubricant → (22.8 iron-plates + 1.4 lubricant)/tile
In my opinion, the costs for the fast underground belts should be doubled. This raises the cost of express underground belts by around 60 iron-plates and results in a price of about 32 iron-plates/tile, which is much better than the nearly identical cost, which they have now. Additionally I would change the amount of lubricant which is needed for them to 16.