1. so expensive as to prevent purchase or use
2. serving to forbid or prevent something

Examples

• The cost of college tuition has become prohibitive for many families.
• Hotel prices in the city center are prohibitive during peak season.
• The prohibitive regulations made it difficult to start a new business.
• Insurance premiums for young drivers are often prohibitive.
• The prohibitive nature of the law discouraged further protests.
• Parking fees downtown are prohibitive for daily commuters.