MyEtherWallet has a slider in the bottom right of the site for gas price:

You can see that it is measured in Gwei, so in this picture you would pay 20 Gwei (20.000.000.000 wei) for every gas unit consumed in the transaction. The gas limit (200.000 for the BAT ICO) caps the amount of gas you allow the transaction to consume. If all 200.000 gas is used, you would pay 20 Gwei * 200.000 gas = 4 million Gwei, or .004 ether ($0.72 @ 180 per ETH).

If you use 30 Gwei for the 200.000 gas limit BAT ICO like me, it will be $1.08 in fees