• 金額きんがく — amount of money
• 総額そうがく — total amount
• 高額こうがく — large amount
• 低額ていがく — small amount / low price
• 多額たがく — a large sum
• 定額ていがく — fixed amount
• 額面がくめん — face value
• 額縁がくぶち — picture frame

額 combines 客 (frame/enclose) with 頁 (head/forehead). It first meant “forehead,” then broadened to framed objects and specified sums — things that are defined, bounded, or counted.

彼かれは 額ひたいに 汗あせをかいていた。
He was sweating on his forehead.

彼女かのじょは 高額こうがくの 賞金しょうきんを 受うけとった。
She received a large cash prize.