diff --git a/config/default.cfg b/config/default.cfg
index 4ce56bdef..8b5941ac4 100644
--- a/config/default.cfg
+++ b/config/default.cfg
@@ -2025,10 +2025,12 @@ cfg$gms$timber <- "default"                  # def = default
 cfg$gms$s73_timber_demand_switch <- 1     # def = 1
 
 # harvesting cost of industrial roundwood per ton of dry matter produced (USD17MER/tDM)
+# based on https://unece.org/forests/prices: 60 EUR/m3 = 72 USD/m3; 72 USD/m3 / 0.6 = 120 USD/tDM
 # * (inflated from default originally in USD05 using USD05 --> USD17 inflation rate: 1.23)
 cfg$gms$s73_timber_prod_cost_wood <- 148            # def = 120 * 1.23
 
 # harvesting cost of woodfuel per ton of dry matter produced (USD17MER/tDM)
+# based on https://unece.org/forests/prices
 # * (inflated from default originally in USD05 using USD05 --> USD17 inflation rate: 1.23)
 cfg$gms$s73_timber_prod_cost_woodfuel <- 74         # def = 60 * 1.23