Regrettable
Disappointing, Precious, Dear
い adjective
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of frugal? It's regrettable or precious. If you're too frugal to buy something your actions are regrettable later when you realize you wanted that thing. If you're so frugal you only buy one single thing, it's very precious to you.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You haven't learned this reading yet so here's a mnemonic to help you:
You made a regrettable decision. You didn't buy that clock you wanted and now it's been discontinued. The salesperson tells you this and all you can say is, "Oh..." (お) really really quietly. How disappointing.
惜しい人を亡くしたものだ。
I lost a precious person.