Function sell_value 

pub fn sell_value(
    goods: &[TradeGood],
    materials: &[RawMaterial],
    tr: &Trade,
    d: Option<&TradeTemplate>,
    material: usize,
) -> i32

What the merchant docked gives for one: with none, its value; else its value for what it buys, three quarters for what it takes, else nothing.

Original: FUN_14005ae80.