I'd also argue that not all 24 are "successes". Belezika, Truelove, Tuohy, Mantack made 8 appearances between them.
Plus, you're stretching "10 years" a touch... no doubt that Chris Taylor and Mark Allott were successful players for us, but they left our youth system 13 and 22 years ago.
Like Singe I think the supply has dried up a bit. Very few of the players offered pro deals now are still here a year later, and not because they've gone on to bigger and better. Tarky is the exception that proves the rule (and maybe Coleman can be one day).