Obviously the money factor is greatest, nothing new.
When I look at Chelsea's 2011-12 squad I struggle to find many genuinely 'world class' players. Ashley Cole. Maybe Terry, Cech and Torres on their day, which doesn't come so often anymore. Yet they won the CL. The difference - they have money to go and spend £100m with no sales in one transfer window.
The difference between our mercato and that of others in Serie A will also be money. We can spend €30m and €6m salary, they can't. So it depends who comes on the market and who we are competing with.
Its not who Chelsea has, but who they can buy, their squad has lacked true impact quality and rejuvenating with potential stars after their past ones are declining. So they just bought the best player in Ligue 1, about do the same for the best one in Portuguese league, and last season when they needed a little kick start, they bought the best La Liga player outside the big two in Mata. They can do quick fixes like these due to financial stature and attractiv nature of their league.
Just like Man U who havent bought much of good players in quite a while, have more or less just gotten Kagawa now, top 3 best player in Bundesliga last two seasons, and can continue on that path if they keep spending, but more importantly, play in a league that can be more attractive for these "potential stars". But yes is naturally about money, money attracts quality and with that comes success, as it was in 90s Italy.
We are one of the few who can financially compete with SOME of these clubs (especially Man U), but we play in a league where sought after quality players are more likely to leave then come to these days.