James 1:21 (NKJV)
To determine what something is worth, there has to be some way to evaluate it. It has been said that one person's trash is another person's treasure, in the sense while one person may not consider something to be valuable, another person sees a value in that thing. But this idea is very subjective and based on personal opinion. The only way to really know if something should be considered trash or treasure is if there is some objective way to evaluate it, by taking personal opinion and preference out of the situation.
There are many standards that could be used to evaluate something, but those standards are often just based on current trends or popular opinion. The only way to know what is truly valuable, what is good or bad, and what is right or wrong is if there is some objective standard to look at. Fortunately, there is such a standard, we have the Bible to show us what is true and false, what is good or bad, and what really is trash or treasure. God's Word has stood the test of time as an accurate standard that can be used to determine what is right and wrong.
So many times, people, even Christians, try to use something other than the Bible as their standard for evaluation, but this is a dangerous thing to do. As James says, we need to "lay aside all filthiness and overflow of wickedness, and receive with meekness the implanted word". Without the standard of God's Word, how will we know what is filthy and wicked, or clean and good? The Bible, God's Word, is the standard for Christians, or it at least should be, and God's Word will show us what is good or bad, trash or treasure.