An eyewatering amount of money is an extremely large one — so large that it gives you a little shock, the way your eyes water when you cut an onion or step into a very bright light. It is not a calm, careful word. Newspapers and ordinary speakers reach for it when a price, a fee, a salary, a fine, or a loss feels far past what seems normal. You will hear eyewatering prices, an eyewatering bill, eyewatering sums. It sits in informal-to-journalistic English; a maths book would just say very large. People sometimes stretch it to other huge numbers (an eyewatering number of emails), but money and cost are where this sense lives. Older and more careful writing often keeps the hyphen: eye-watering.

天價的、高得驚人的（金額）