Function alter_cost

src/shk.c:3236–3256

called when an item's value has been enhanced; if it happens to be on any shop bill, update that bill to reflect the new higher price [if the new price drops for some reason, keep the old one in place] */

   on any shop bill, update that bill to reflect the new higher price
   [if the new price drops for some reason, keep the old one in place] */
void
alter_cost(
    struct obj *obj,
    long amt) /* if 0, use regular shop pricing, otherwise force amount;
                 if negative, use abs(amt) even if it's less than old cost */
{
    struct bill_x *bp = 0;
    struct monst *shkp;
    long new_price;

    for (shkp = next_shkp(fmon, TRUE); shkp; shkp = next_shkp(shkp, TRUE))
        if ((bp = onbill(obj, shkp, TRUE)) != 0) {
            new_price = !amt ? get_cost(obj, shkp) : (amt < 0L) ? -amt : amt;
            if (new_price > bp->price || amt < 0L) {
                bp->price = new_price;
                update_inventory();
            }
            break; /* done */
        }
    return;
}

/* called from doinv(invent.c) for inventory of unpaid objects */
long