Function price_paid_job 

pub fn price_paid_job(
    production_cost: u64,
    roi_cap_percent: u64,
    max_roi_percent: u64,
) -> u64

Fair price for a paid job: the audited production (energy) cost plus a capped ROI margin (the extraction guard), via commons_cost. The price never exceeds production_cost × (1 + max_roi%).