安い

1. Origins, structure, and basic meaning

• Structure: 安い (やすい) is an adjective for low price. 安い predicates a price; 安く adverbially modifies a purchase.
• Basic usage: One sentence directly calls vegetables cheap; the other says shoes could be bought for less than expected.

2. Common pitfalls and similar expressions

• Predicated product price and manner of purchase
  • 野菜が安い evaluates goods as subject; 安く買えた modifies the achieved purchase. These examples do not establish low quality.