The value of "old" comics depends on what you mean. Some old comics such as Spider-man number one continue to increase in value (worth maybe $125,000 right now). In general, the value of "old" comics depends on supply and demand. If a comic is rare AND people desire to own it, the value increases. For most comics from the 1980s onward, they are not rare, so they are not worth much money. New comics is different. The price of new comics is like the price of any new item. Its cost is based on how much it cost to make it. All the costs involved -including paying writers, artists, inkers, letterers, paying for printing, paying for paper, etc, go into the price of new comics. Because of INFLATION, the price of all of these go up, and so then do the price of the comic books. INFLATION exists because of CAPITALISM. In a CAPITALISTIC economy, the rich people always try to get more and more richer. For example, if a company makes 1 million dollars in profit in one year, they want to make 1 million one hundred thousand dollars in profit the next year. This is a 10 percent increase in profit. Then the company can say they grew by 10 percent. However, for most items, only the same number of people buy the item every year. So, for the company to make more money the next year, they need to raise the price of the item. Hence prices always increase.

Pook's basic answer to the question is exactly right. The following digression into economics is not. Let's stay "on message," folks!