无论多少数量，这个费用是不退还的 英文怎么说啊

"Regardless of the quantity, this fee is non-refundable." 是更常见的表达方式。你的翻译也基本上意思通达，但语法上有几处小错误。应该是 "No matter how many in quantity, it cannot be refunded." 或者 "It is not refundable, regardless of the quantity."。