Is it? Unless the team has a TV blackout, then in fact the ticket prices are not too high as demand has outstripped supply. I would argue that for any team with a ST waiting list that is more than 1% of stadium capacity the ticket prices are too low and should be raised until the waiting list vanishes.
I think you're oversimplifying. Your argument would be sound if the gate was the only product the business sold. It isn't, and I'm not convinced that the other products are completely independent. If fans feel they're getting gouged, will fan numbers drop? If parents can't afford to take their children, will it affect fan numbers long term? Will lower number of fans affect merchandising sales? Will a lower "level of fandom"?
Will overall lack of support in the local population (those most affected by ticket prices) hurt the chance the team has of securing public funding for a future stadium?
Profit maximization is about maximizing the whole enchilada, not just gate receipts. I'm convinced team owners have a very good reason to keep fans at least reasonably happy.
Businesses often fail to take a long term view, focusing instead on short term profits. The NFL as a whole is exceptionally popular and this has allowed the business an unprecedented amount of freedom in raising prices for everything associated with it. Total revenue has more than doubled over the past 10 years (and that's not including massive amounts of public funding for stadiums) and, don't kid yourself, there's only one source of revenue. The NFL could easily be undercutting its future fan base without it showing up in current profits.