That's not the principle in play, where Rick Perry is doing tolling in Texas. From a TexDoT slide used in their own presentations concerning the NAFTA Highway (NASCO Corridor, Trans-Texas Corridor), one of the ruling concepts of tolling is that for the tolled asset to work, viable non-tolled alternatives -- competition -- has to be eliminated, in order to protect the revenue stream of the toll road operator.
And as a further matter of public record, the head squeeze at Texas DoT has been quoted on the subject of tolling as saying, and I quote, the future of Texas is "Toll roads, or slow roads, or no roads!!"
Nice, catchy, medieval-sounding little slogan, don't you think? You could almost do one of those "Dark Ages" Capital One commercials with that, couldn't you?
It's also worth noting that tolling a highway on a major trade corridor makes a lot of sense for simple economic/operational reasons -- because it forces users who have both a start and end point outside the region to pay for their use of the system.