The clubs involved in this season's Champions League and Europa League group stages invested more than half of their transfer spending in the last window on players aged 24 and under, a report by European soccer body UEFA said on Thursday.
UEFA's club competition report said the 80 clubs spent a combined $3.98 billion in the summer window, with 43 percent of them breaking their own transfer records.
But instead of splurging on more experienced players, they spent a record 64 percent of that money on players aged 24 or younger, and only 7 percent went on those over 28.
Defenders and forwards each made up 35 percent of expenditure, midfielders 25 percent and goalkeepers 5 percent, it said.
But while spending was high, clubs were also busy selling players, and transfer earnings totalled an estimated 3.72 billion euros.
Many clubs outside the main leagues, in countries such as Switzerland, Portugal and the Netherlands, now have a financial model based on buying young players, developing their talent and then selling them on to bigger clubs several years later.
UEFA said that six clubs managed net earnings of over 50 million euros in their summer transfer dealings.
The report also illustrated the disparity in spending power between clubs, when it said that clubs had spent anything between 250,000 euros and 953 million euros in assembling their current squads.
Other stats showed that Portugal has nine of the 80 coaches involved, a large number given the country's size and population. That is followed by Spain with seven, Germany with six and Netherlands, Italy and France with five apiece. England has only two coaches involved.
Ajax Amsterdam were the most prolific scoring team with 3.5 goals per game in winning the Eredivisie, and Shakhtar Donetsk had the stingiest defence with just 0.34 goals conceded per game.
Around Europe, English Premier League champions Manchester City were the fourth-most dominant team in their own league last season with 2.58 per points per game.
The mantle of the most dominant team of all, however, went to the mighty guns of HB Torshavn of the Faroe Islands league, who averaged 2.70 points per game with their domestic record of 24 wins, one draw and two defeats last season.