もんさ

that's just how it is

→ もの
phrase Rare #26,160
that's just how it is A colloquial, emphatic sentence ending derived from ものさ. It can express assertion, resignation, or reassurance, often with a masculine or somewhat old-fashioned tone.
JA: そんなこと、誰にでもあるもんさ。
EN: That kind of thing happens to everyone.

安いもんさ

It’s cheap, after all.

— 恋する惑星 (1994)

あんな美人あのアホ世の定めってもんさ

A beauty like her ending up with that idiot—such is fate.

— いまを生きる (1989)

大したもんさ

That's quite something.

— グッドフェローズ (1990)

どっちにせよ一人の人間が一生うちに触れる情報なんて僅かもんさ

Either way, the amount of information any one person encounters in a lifetime is minuscule.

— GHOST IN THE SHELL (1995)

実は見た目よりしっかりしたもんさお前が相手じゃ勝ち目は無いからな

Actually, I'm tougher than I look. You don't stand a chance against me.

— オープン・ユア・アイズ (1997)

ヒドイもんさ

It's pretty awful.

— ジョジョ・ラビット (2019)

会いたい奴は会えるもんさ

If you really want to see someone, you’ll find a way.