The very foundations of Finance are built on sand
What do I mean by that? Finance is built on the concept of value, or worth. "How much is this gold worth?", "how much is the client willing to pay for this service?"
The concept of value and worth are subjective. They are in the eye of the beholder:
If you ask a thirsty backpacker stranded in the middle of the Sahara: How much are you willing to pay for a 2 litre bottle of water? The answer, most likely is many monies & possible limbs.
Now trying flogging the same water to city trader in a champagne bar.
I can hear you scoffing, "Oh but that's a silly example, the backpacker was practically dead" Correct, worth is subjective. Its based on your circumstances. There are many other examples, the Turner painting in a jumble sale, the sale of a sports car when the wife becomes pregnant, etc, etc.
Complex derivatives are really not complex. They are normally a "RAID" of different types of contracts. What then happens is the end user is deliberately bamboozled into not asking questions.