Well, they need that lumber, or they don’t?
In any case, they won’t be getting any for 50g
I.e. modifier to purchase price from the lumber mill does not make sense during “Rebuilding effort” effect. If town actually needs that lumber
I see “low supply” part as referring to a penalty to stock generated, but that does not mean that prices should not be adjusted in accordance to the high demand & low supply situation.
In any case, description is too vague. If that is intended, imho it needs to be more clear on what exactly it does.