Trigger Performance Impact When Not Firing?

I'm trying to find some information on the performance impact of a trigger on a heavily updated table when the condition to fire the update trigger is NOT met. In other words I guess what I'm really trying to find out is what the performance impact of the system checking the condition on the trigger to determine if it should fire or not is.

For example I have a batch job that inserts and updates a table heavily, but the batch job almost never updates the column in question on the trigger to the value that would cause it to fire, but it does update that column to other values often.

I know about the many downsides of using triggers in general, but I'm working with a third party application, so more optimal solutions aren't an option.