Preseason ticket prices are a joke and even the NFL realizes that, which is why they were trying to force the players into playing two more games a year when many are already dying prematurely from 16, not to mention that it would ruin the record books AGAIN. The NFL identified that it was a problem, but since lowering ticket prices for anything is apparently unfathomable, they tried to force a different solution.
These days, concerts and everything are becoming more expensive, but the irony is that there are so many ways to enjoy quality entertainment in your home these days that people are much less inclined to want to pay high prices. The markets for a lot of things are going to continue to get smaller and smaller as the industries try and extract more and more from the people who still want to go, thus causing their markets to shrink even further due to low prices.
Someone earlier in this thread said that demand for NFL tickets was high, but that's really not the case. There is proof all over the NFL that demand is shrinking, both due to economic reasons and to quality home viewing of multiple NFL games at once, but instead of ticket prices matching demand, ticket prices are still being raised to try and maintain the same level of ticket income as there was when there was actually a lot more demand.