Sorry I mis-read your question. the close price doesn't mean much. You need to look at the volume of the trading. for SGN, if you want to buy a lot for 300,000, you would have to pay much higher - the volume is just too thin...
Look at the market depth of SGN now, if you want to buy 160,000 shares, you would have to pay $1.25 for it. Not so many people are selling