I've been doing some research on futures, and I was surprised to discover the prices for natural gas future (NG) and the natural gas e-mini future (QG) are nearly identical. Prices for the last year are plotted in the attached notebook. As you can see, the prices differ slightly at the beginning of the plot, but even this difference disappears if you specify no adjustment when creating the continuous futures. I was expecting a price difference on the order of a factor of four given that NG is a contract for 10,000 million BTU and QG is a contract for one quarter as much. I'm curious as to why my intuition for the prices was so mistaken.