I honestly think there has either got to be a huge price difference or a major gain in fuel mileage for these mini trucks to become real players on the truck market.
No, I don't think there has to be a "huge" difference in price OR mileage for compact/midsize trucks to be competitive with full-size trucks. Some folks JUST DON'T WANT a full size behemoth of a truck, and would happily buy an
equivalent midsize instead - even if it was the same price as a half-ton, and the mileage was comparable. Just the fact that a midsize truck is a more manageable size could sway a lot of buyers who need some utitlity, but not full-size capability.
But the problem is that those full size behemoths have all the latest technology, most advanced powertrains, most configuration options, and are priced competitively against each other. The midsizers have no competition and thus no incentive to improve. Frontier? Ridgeline (not even a real BOF truck)? GM debacles? No Ranger? No Dakota? As AS pointed out, Toyota is happy gouging the Taco fans as long as they have nowhere else to go.
So your choice is to take an old-tech, unrefined, outdated, overpriced midsize truck (that would otherwise meet your needs nicely), or a much more current, competitively priced full size truck that is larger than what you would like. It doesn't mean that there's no market out there for compact/midsize trucks - but the market for overpriced, outdated small trucks is justifiably small!