Used for amounts, prices, competition, or demands that go beyond what is reasonable or appropriate. Often appears in formal or business contexts.
That hotel demanded an exorbitant fee.
We cannot accept excessive demands.
I think this price is exorbitant.
Competition in the market has become excessive.
過剰 stresses there being too much of something in quantity (e.g. 過剰生産), whereas 過当 stresses that a price, demand, or level of competition has gone beyond a reasonable standard.
法外 carries a stronger, more emotional sense of being outrageously beyond normal limits, while 過当 is a calmer, more formal way of saying something exceeds a reasonable standard.
適正 describes an amount, price, or level that is fair and appropriate, the opposite of 過当, which describes one that is excessive and unreasonable.
excessive competition; cutthroat competition
Compound of 過 (exceed) and 当 (appropriate), literally 'exceeding what is proper'.