Just to be clear, the total cost of the companion ticket is not just $99, it's the $99 plus whatever the original taxes and fees are on the ticket as well. Also, on the Gold Delta Amex companion cert, it's only good on L, U, and T fares. Just an fyi.

That is a very good point. I recently booked 2 tix using the companion coupon and the 2nd ticket was $143. Still saved me about $150 though.

Fare: 99.00 USD
Tax: 44.23 TX
Total: 143.23 USD