Setting the costs by using the id from BaseCosts Table and the value n of the following formula:

Using math: NewBaseCost = OldBaseCost * 2^(n-8), where n is the value of property 08.

You can only rise base costs by factors which correspond a power of 2. The general way to set parameters are in pairs of two:
<base cost no> <exponent of multiplicator>
where
<base cost no> is an entry from the first column of the base cost list
and
<exponent of multiplicator> is the n in the multiplicator to the original base costs: 2^(n-8) Thus a value of 8 will leave the costs unchanged, a value of 9 will double it, 10 will quadruple it and 7 will half it.

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Discussion: http://www.tt-forums.net/viewtopic.php?t=46720

Examples

config for raise Terraform (x16), but keep foundations on default:

using Pikka's pb_build but modify foundations:

other similar grfs are:

- Pikka's "Modified Building Costs" (doesn't respect the new OpenTTD feature which splits terraform and foundations)

- Terkhen's "Raise landscaping costs"

- my old grfs: BaseCosts Mod 2 and Airmod