They were able to bring in several young players at prices that were not that expensive but within few years these young players could have extraordinary playing skills, this is why Serie A has team that has been able to win important competitions such as the UCL several times.
Look at how Juventus, Inter Milan, AC Milan always show their mainstay players, in the past, these three teams were the best at developing players and making the players become list of great European players.
I agree with you. In fact, I have never heard of a Serie A team that has a lot of money to buy star players. Many player transfer records are often broken by La Liga and English League teams. But they are still able to produce great players and become one of the best European leagues. Next season Italy has 5 clubs that will play in the Champions League. They are in second place for coefficients. This proves that Serie A clubs are great even though they do not have rich financial backing.
Take a look at the picture
The image depicts a list of serie a teams with the richest owners at this moment. To be honest, clubs such of Roma and Fiorentina are owned by the second and third richest owners, respectively, but they remain stingy when it comes to signing new players to bolster their squads. No doubt that jose mourinho was always complaining toward roma's management last season Sometimes the owner does not care how well their team performs.
They are just concerned with generating profit for their team through football transactions. As you can see, no large teams are featured on that list. Even as a new team in serie A, como 1907, it is owned by the richest owner in the league when compared to the other major clubs.