我不买了。

Use it when the price is too high. Use it when you realize you don't need that third cat-shaped mug. You just say 我不买了 and the conversation ends. It is a complete sentence on its own. You don't need fancy grammar here. Just subject, negation, verb, and that final 了.

You will use this most at street markets. It is the perfect way to end a bargaining session. If the seller won't budge, say this and start walking. You can also use it online. If a friend asks if you bought those shoes, tell them 我不买了. It works for big things like cars or small things like apples.

Don't use this if you have already paid. That is a refund request, which is different. Avoid using it in very high-end boutiques with a harsh tone. It might sound a bit blunt there. In those cases, add a 'sorry' or 'let me think' first. Don't use it if you never intended to buy at all. That is just 'looking,' not 'not buying anymore.'

In China, bargaining is a social dance. 我不买了 is often a tactical move. It is the 'walk-away' power move. Sellers often drop the price the moment they hear this. It shows you are a savvy shopper who knows your limit. It is not considered rude if said with a neutral face. It is just part of the business game.

You can make it softer by adding 先 (first). 我先不买了 means 'I won't buy it for now.' This saves face for everyone. If you want to be very firm, say 我不买了，太贵了 (I'm not buying, it's too expensive). For a more polite version, try 不好意思，我不买了 (Sorry, I won't buy it). It keeps the relationship friendly while closing your wallet.