So here are the facts on all those "fees and taxes" (which, as usual, are left out when people make these claims). It's a 7.5% Excise tax and it is charged on domestic flights only. That's it. The rest of the taxes and fees are fixed amounts and do not vary with the base fare. Note that since BE and C+ are separate fares, so DL does pay the 7.5% taxes on the upcharge amounts when going from BE to MC to C+. If they were really so determined to avoid the 7.5% tax, why didn't they leave C+ as a separate add-on fee rather than make it a higher fare?