Something can be priceless personally and worthless commercially.

Worth splits into two unrelated measures. What something will sell for depends on what strangers want; what it means to you depends on your history with it, and those two numbers have no obligation to resemble each other. A letter, a worn object, a place with nothing remarkable about it can carry everything and fetch nothing.

Be careful about letting market value tell you what to keep. And be equally careful about assuming other people should see what you see in it. Both are private, and that is fine.