Final answer:
The cost of debt investments includes interest payments, principal repayments, and dividend payments, but not capital gains.
Step-by-step explanation:
The cost of debt investments includes interest payments, principal repayments, and dividend payments. However, it does not include capital gains. Capital gains refer to the increase in the value of an investment over time, which is typically associated with equity investments such as stocks. Debt investments, on the other hand, involve lending money to a borrower and receiving fixed interest payments.