Next to nothing? I guess your standards are pretty fucking high here. There are multiple players in Serie A who have been Inter youth players. Getting to Serie A level is IMO pretty fucking good in the end given how many players there are eventually not making it to highest level of that particular country.
And the problem is not so much that we aren't playing our youngsters, but that we're paying a lot of money to bring scrubs that are barely any better than them. It's pretty simple our former and current youngsters may not be good enough to be sure starters but they certainly are good enough to be backup players.
Also we really need to stop going for "Serie A proven players", it never really pays off, like the chances you get a Serie A proven player for a reasonable price is slim to none, unless it's a free agent. Napoli built one of the best teams in Europe with somewhat cheap players mostly from other leagues Min-jae Kim (€16M), Anguissa (€16M), Zielinski (€16M) and Kvaratskhelia (€12M), basically only Osimhen (€75M) was super expensive for them.
But Inter wants to keep on buying only known players, if you want to do that you have to spend hundreds of millions of Euros every season. We need to start looking for relatively unknown young talented players and fill the gaps with our primavera and some free agents.