Two points.
One is about the stock price (valuation) and other is about the dividend (wage x contract).
Clearly, if you pay a player $100,000 p/y for 3 years, contract is worth = $300,000 and look to recoup when selling. This is the dividend.
The stock price is what demand and supply laws govern regarding player market availabilty and finances of the buyer.
You'd think a players attributes/persona would be the governing laws for valuations, and not club and league reputation.
You might argue, as my left and right brain often do, a players value should decrease with age, as option contracts do, but, if a club wants to buy a player for instant gratification with a short term goal, that's their decision.
Clubs don't have to sell and clubs don't have to buy.
Reason I write this, if I buy a burger at McDonalds, it will taste the same whether I eat in a poor housing commission house or a rich mansion.
Perhaps there should be a fair wage and valuation commission to stop potential exploitation.