Somebody pays for those airport access roads. Depending on the exact nature of the locality, it's part of local property taxes, bonds, per ticket fees and so on. DFW chooses to collect those fees from the people who use those roads. That's good government, not anti-consumer.

The reverse of this is the SFO-BART vs. IAD-Metro example. BART charges an extra fee for the use of the SFO stop to defray the extra costs associated with the airport stop, so that San Francisco area commuters don't get socked with those extra costs. BART is conveniently located and nobody minds the extra fee. IAD, on the other hand, refused to implement the extra fee when it designed the Silver line, so rather than increasing the costs of construction and imposing a surcharge for the IAD stop to have the Metro run into the terminal, the IAD stop will now be across a parking lot. When the line opens, we'll see how many people getting off an international flight lug their stuff across that lot (even if there's a handy automated walkway).

No free lunch.