The key point, which has been said many times in this thread is that the Pats are not like any other franchise. I think its easy to say that its only 500k, or .4% of the overall cap, but you also have to look at this in real world terms as well.
There are countless teams that wouldnt want to deal with the headache of bringing in a player, who will not add any value to the team on his current contract, to have time energy and resources put towards him hopefully become healthy, but still may never recover and play for your team. It may seem like simple use of resources that already exist in-house for the money each team is aloted, but its not that simple.
Another coach might be concerned about an angry Aaron Hernandez fuming in his office that they are paying someone with no current value more than him, while Hernandez plays his heart out each week. You may have an assistant coach like Pepper Johnson who has been here for 12 years not getting a raise(hypothetically), yet a 4th TE is getting paid to do nothing but sit. That is with nothing to be said about morale for lower positions in the organization like equipment managers, masseuse's and chiropractors. A poorly run organization with no internal integrity can constantly face questions from their own people about where dollars are going, or why their person share is so small in comparison to someone who brings nothing at the moment to the current team.
These are questions we have been taught not to worry about, with the Krafts and Belichick running this franchise and team. Belichick never allows salary or perceived value (jersey sales/name recognition) justify keeping or relieving them of their duties. We follow a team where we dont need to worry about our other star TE getting upset by a move like this, simply because, there is no room on this team for behaviour or attitude like that. But it happens elsewhere, we have just been spoiled with a lack of spoiled kids.
Thats the difference. Its not about a 4th TE. Its not about if he will be healthy. Its not about other players contracts. Its simply about the team not allowing a valuable future resource to get away because they are afraid of how it will effect other players, or other teams opinions. Its not about one player, its not about any other team. Its about one team, and making the best one possible.
I am not sure what surprises me more, that 30 teams didnt think that risk was worth it, or that the defending champions thought 31 thought that way.