A Ponzi scheme is a form of fraud that lures investors and pays profits to earlier investors with funds from more recent investors.
Early investors are not paid profits from recent investors. Any investors can take profits from any other investor by trading at the right time.The scheme leads victims to believe that profits are coming from legitimate business activity
Satoshi never told anyone that they were going to make a profit at any time, and indeed, many early investors lost money via electricity and hardware costs mining an asset which was worth nothing at the time.and they remain unaware that other investors are the source of funds.
There is no secrecy at all about what gives Bitcoin value or how the market is pricing it at any given time.People compare bitcoin to a Ponzi scheme because the price increases when more money flows into the underlying asset.
This is a pointless definition. The value of anything increases when more money flows in to the thing in question. Property, stocks, shares, bitcoin, gold, art, oil, wheat, cows, onions, you name it. 
