To find the total price when two medium one-topping pizzas are purchased with the incentive, we will use the price given for the two pizzas option.
The incentive states:
- 1 one-topping medium pizza for $7.99
- 2 one-topping medium pizzas for $6.49 each
To calculate the total price for 2 pizzas using the second option:
\[ \text{Total price} = 2 \times 6.49 = 12.98 \]
Therefore, the total price when purchasing two medium one-topping pizzas with the incentive is $12.98.
Based on the responses, the correct answer is $12.98.