Thinking is an essential cognitive process that often goes unnoticed in our daily lives, yet it requires significant mental energy and time. The 'cost' of thinking can be viewed not only in monetary terms but also in emotional and physical aspects. For instance, prolonged deep thinking can lead to mental fatigue, stress, and a decrease in productivity if not managed properly. Many people undervalue the power and effort of their own thoughts, sometimes even wishing to 'sell' their mental ideas or intellectual labor without recognizing the true worth behind it. Cognitive work, whether it is problem-solving, creative thinking, or decision-making, contributes heavily to personal and professional growth. In recent years, psychological and neuroscientific research has shown that thinking consumes more energy than many physical tasks. The brain, although only 2% of body weight, uses about 20% of the body's energy resources. Therefore, engaging in critical thinking or complex mental work is indeed 'costly' in terms of energy expenditure. However, the value of thinking cannot be reduced solely to its cost. The outcomes of thoughtful processes—innovations, solutions, strategies, and creativity—often lead to great rewards, be it personal satisfaction, financial gain, or societal advancement. Understanding the cost and value of thinking encourages mindful engagement with mental tasks. People may choose to invest their time and energy more efficiently, balancing periods of intense thinking with rest to maintain productivity and well-being. Ultimately, reflecting on questions like 'How much thinking is cost?' and 'Who’s interested to buy it from me?' invites us to appreciate the importance of intellectual effort and consider how we monetize or utilize our cognitive abilities in daily life and career paths.