I don't think so. We're worried about not being able to pay someone to perform the job admirably because we're overpaying someone else who is not performing the job admirably. Whether we like it or not, an NFL team is restricted by a salary cap, and if you're overpaying people who are not worth that much, you won't be able to acquire someone who IS worth it.
Fans who pay any serious attention to what their team is doing are naturally going to be concerned when their team signs an expensive contract to a player who underperforms.
Those salaries are not secret, they are made publicly available. If part of becoming a quality team means properly managing their salary cap, then why shouldn't fans be concerned about the same thing?