Yes, many don't understand the Academy has a secondary function. There are plenty who we'll pick up for £1m and sell on a couple of years later for £4m after a successful loan spell. This in time will probably prove more common than developing first team players
Yes, at every step up in age group for a young player, about 1 in 10 will make that step up. A club has to trawl through a thousand young players to find one which will play for the first team.
It's further complicated by the fact that some develop at different rates, so from time to time...