Like many in this thread, I don't pretend to understand the business model which justifies seven figure deals to rising high school juniors who aren't (currently) very famous. That being said, I didn't (initially) understand the business model of many ventures that now appear quite successful (Google, Facebook, Twitter, Netflix, Bitcoin, NFTs, the Khardashians, etc).
If as you mention, the organizers are somehow getting a cut of future earnings, I can see a better rationale for these payments. I can imagine a sports agent advancing a top level prospect a significant sum of money to sign a long term deal, even if the earnings a limited for the first few years.
For example, consider the
Top 30 RSCI prospects as of the Summer before their senior year in High School. As far as I can tell, the sum total of the guaranteed NBA contracts (past and future) for the top 30 players in this relatively weak class* is $618,931,415. A savy investor could probably make a good business case for paying considerable sums to these type of players in exchange for a cut of future earnings.
*The top 10 players in this class (prior to their Senior year) were Ben Simmons, Jaylen Brown, Malik Newman, Chieck Diallo, Ivan Rabb, Diamond Stone, Skal Labissiere, Chase Jeter, Caleb Swanigan, and Alonzo Trier).