Its that old argument about the bean counters knowing the cost of everything and the value of nothing. There is I suppose a comprison to the decline of University Air Squadrons (There are now fewer and the students get less flying), or the demise of Air Cadet Gliding.
The VALUE is that you produce a generation of individuals, many of whom move on to play decisive roles in society and think highly of the military.
And of course if the individuals were not attending Welbeck then they would be attending 6th form somewhere else so although the Army would not be paying, the government would.