Extremely high, to the point of being prohibitive.

So expensive that it prevents someone from purchasing.

अत्यधिक ऊँचा

English Usage: The costs of the project were prohibitively high for most investors.

Hindi Usage: परियोजना की लागत अधिकांश निवेशकों के लिए अत्यधिक ऊँची थी।

Extremely difficult, making it nearly impossible to achieve.

अत्यधिक कठिन

English Usage: The exam was prohibitively difficult for students without prior knowledge.

Hindi Usage: परीक्षा उन छात्रों के लिए अत्यधिक कठिन थी जिनके पास पूर्व ज्ञान नहीं था।