Sustainable for how long? 5 years? 10 years? The long-term? The Premier League has become what it is not because of traditional football supporters, but because it's become the trendy thing for the posher classes. Within my lifetime, when I applied for a job I was told in no uncertain terms NOT to put football supporter on my list of interests because I'd been seen as the "wrong sort" by a potential employer. Now I hear tales of interviews where they ended up chatting about the state of the Arsenal more than they did about the job! Football can be dropped again, and a unique factor in English football has always been the pyramid structure which sees teams way down the leagues still playing professionally and attracting good numbers to watch them. That's disappearing and, the more the greed continues in the top level, the more it filters down such that many smaller clubs will not be able to compete any more.
So, there's the benefit of "making less money from a full ground". The bigger picture. As I said first time, what about the Bundesliga? The biggest clubs charge a fraction of Premier League prices and fill their grounds (highest average attendance in Europe), yet they make a profit despite broadcast income being a fraction of the Premier League. They pay less out in wages as a percentage of revenue than the Premier League yet few would argue that the standard isn't as good. We keep peddling this lie that the Premier League has to keep paying more and more to attract players, it's just not true.