• A bundle (informal) is a large amount of money.To make a bundle is to earn a large amount of money.
• a bundle とは、多額のお金をさす、くだけた表現です。make a bundle は、多額のお金を得る、つまり、大金を儲ける、という意味です。

examples

1. She’s going to be a very wealthy woman if she ever decides to sell her business. It must be worth a bundle.
2. You can save a bundle by buying groceries in bulk (= in large amounts).
3. The store looks great now, but the renovations sure cost a bundle!
4. I made a bundle in the late ’80s trading commodities futures.