Well that would be true if La liga are counting in Spanish talent pool alone (and of course there will come a time when it drys out again and the amount of talent will decrease ) however this is not the case.. La liga clubs scout all over the world so you have young talents from Brazil , Colombia , Argentina , France , Netherlands.. it's all about having a good eye for talent
If you look closely you have Varane who is young and cost us peanuts (could have been bought by any medium size club not just RM ) , you have Griezmann another French hot shot in Sociedad , Raktic (the Croat ) who has the highest assist in the table after a selection of Barca & Real players , Carlos Vela (Mexico) , Diego Costa, Jonas Babtistao (Brazil ) Feghouli (Algeria )
Overall we are getting better results for the scouting talent compared to the EPL , Bundesliga , Dutch, French(apart from Africans & north Africans or originally were before they got the nationality )
Those pin point eye for talent allow the Spanish clubs to make one hell pot of money from the other rich clubs (Barca & Real included ) the only team that can match La Liga is actually Porto followed by Benfica... (I think it's an Iberian thing ) but when you look at Seville who bought Alves for 400 K and sold him for 35 Million to Barca now that's business , eventually those players return to those clubs if they didn't adapt to the high pressure and for peanuts costing Barca and Real a lot and other clubs too (see Canales , see Riquelme , see Forlan etc) eventually things even out but the Spanish clubs stupid owners / presidents waste money on other stuff