I really don't think evaluating a league in terms of salary speaks to its "toughness." You could have a team that is top heavy on salary because they have high ratings in the "sexy" categories, but the manager isn't tactically very good. Having several marginal managers in this setting would produce a league with higher tv revenues, and talented players, but that doesn't make it tough.
I think rank is a much purer rating system. A manager who can succeed with a lower salary, and consistently beats teams he shouldn't, is going to have a higher rank long term.
Which leads me to my league where we have several sub 100 teams, half of our league under 160, and we even a former NBBA team. It's not uncommon for a D2 demotee to find himself stuck in the middle of a competitive upper echelon, or even to miss the playoffs altogether. Managers in our league consistently use several strategies both offensively and defensively and our Season 14 champ made the Finals the next year in D2.
I'm done with my PL next week if there is still room I'm game for participating.
Rip