To make a profit, it is like stock market pump and dump schemes.
In a stock market people use the pump and dump scheme, all you do is buy cheap stocks. Say these stocks will increase in value to 10x the cost they are, so people buy them to make a profit. You then see the price increase and when they have increased loads you just sell all your stocks at 5x what they were originally worth. PROFIT (although anyone who buys the stocks will miss out as the stocks will crash to below what they were worth before)

So in bitcoins you get a cheapcoin by mining or buying hype it up the cost increases you sell out and PROFIT.

Same scam but in a different place.