I'm a newbie to trading futures coming from the stocks world 
With stocks as the price goes higher it becomes more expensive to buy something and vice versa. It doesn't seem to be the same with futures? ie. does purchasing a Russell 2000 E-Mini contract (ERT) *always* cost $500? If the Russell index rises a number of points later in the day wouldn't it cost more per contract, or am I missing something?
Thanks for any clarification or pointers to where I can find information about how this works!

With stocks as the price goes higher it becomes more expensive to buy something and vice versa. It doesn't seem to be the same with futures? ie. does purchasing a Russell 2000 E-Mini contract (ERT) *always* cost $500? If the Russell index rises a number of points later in the day wouldn't it cost more per contract, or am I missing something?
Thanks for any clarification or pointers to where I can find information about how this works!