A-M's brilliant, yet humble Xhaka-stan 😍
How about simply using the leagues overall squad cost and how that has increased over time? With that metric you could also look at the relationship between the top 4s squad cost compared to the rest of the league and how that ratio has changed over time.The thing is when discussing if the league is hard nor or before the same points people use to justify their positions can equally be used by the opposing party to refute it. It's a tricky thing to discuss imo, I don't even know where to being to get even a semi-objective/quantifiable metric of how you would judge it.
If we agree that squad cost has a strong correlation to squad quality and to where your team should end up league position wise, then this is the metric to use. As so much money has been pumped into the league over the period it should in my view have improved the overall quality of the league.