What happens to price when supply and demand increase?

Well it should go up, say a Xbox 360 costs £200 and there are 200 available and 200 orders prices should increase a little so it may cost £210 but if there is 200 orders but 150 360's the price will increase to the extent that who ever is willing to pay more will get one.

Conversely if there are 50 orders and 200 xboxes then the price should fall.
This is a simplification of course. There are other factors involved.