Function sell_gold

pub fn sell_gold(
    eff_level: f64,
    quality: f64,
    cfg_exp: Option<f64>,
    cfg_coef: Option<f64>,
) -> i64

BAL-008 sale price: round(G0 × eff_level(snapshot)^α × M_quality).

The shape differs from sell_price_with_config in a way that is easy to miss: the quality multiplier is linear, OUTSIDE the exponent. The old form raised the already-multiplied eff_by_level × rarity_q to α, which re-prices rarity by α as well; the signed table assumes rarity scales the price directly. Feeding the pre-multiplied eff into the new constants would look right and produce quite different Gold.

Depends only on snapshot Character Level and quality, so two items of the same level and quality sell for the same regardless of their ±10% stat roll, optional stats or power_bonus.