Function screeps::game::market::calc_transaction_cost

pub fn calc_transaction_cost(
    amount: u32,
    room_1: &JsString,
    room_2: &JsString
) -> u32

Get the amount of energy required to send a given amount of any resource from one room to another. See TERMINAL_SEND_COST_SCALE for information about the calculation.

Screeps documentation