Money today is worth more than money in the future. Most investors want to earn a 8-14% annual return over the life of a note and the longer the note, the deeper the discount will be in order to earn that return every year. That’s why a 10-year note is worth more than a 30-year note. Quality is also a factor. If the note is low risk, the investor will be willing to buy it at a lower yield and thus pay more cash for it today. Notes with a high level of risk will merit a higher yield and will be discounted more.