Here we go again. The cosy Armchair world which is devoid of common sense.
Let me try.
You sign a young lad that seems to have bags of potential. He costs nothing to bring onto the books. He has no agent, not contractually bound to any other club. His wages and costs are minimal in comparison to your first team stars. BUT he trains with you every day. You get to know the players style, ability, attitude, fitness levels and weaknesses. YOU mould him into the best player he can be perhaps, YOU mould him into a player that fits the system and style of your club. that player becomes a perfect fit or perhaps he doesn't but his skills are recognised by other clubsand he becomes wanted by those clubs you decide to sell. Profit all the way to the bank. Perhaps this lad turns into something truly special and despite your best efforts he wants to move to Barcelona. Again it's profit all the way. Perhaps you do manage to keep him. Young lad, come through the system, fits your clubs style perfectly he becomes the heart of the club. Marketing profits sky rocket thanks to ths player. Again it's profit all the way.
Alternatively, you ignore the youngsters and decide that the only way to improve is to buy your way up the league. You buy in two, maybe three top top players. You have to pay over the odds for them. Not in transfer fees but to their agent and in wages as you might not have Champions League football to offer. Very quickly you find that something is wrong, they don't ft your system, perhaps they're a bit lazy and just happy to receive their fat pay cheque. Shirt sales were good fo a while butthe press soon jump on your back asking why this £40m player is on the bench. It gets to a point where you sell your £40m player for £20m. Your realise you've made several mistakes. 1. You paid for a player that wasn't a fit for your club. Everything hinted that he might be, but sadly no. 2. You didn't know he had such a poor attitude to training 3. He sdidn't settle in the area 4. You've lost way more than £20m. His wages, signing on fees, agents fees have cost you a massive fortune and this player has contributed very little to fist team success and harmony.
You wish you could have signed this player as a youngster!
Young players / youth is they forward. It's always been that way. Don't let the mega signings that go on distract you from that. The trick is to identify players that will contribute to your club as early as possible. Be that as a school kid or perhaps someone taking their first steps in the pro game. Notice how youth signings are a much higher profile in the press nowadays. Everyone's trying the same thing, which increases their price further. The only way to really short cut that is to create your own as Barcelona have done.