'Worth' is arbitrary, not absolute. What you are describing is 'what is worth to you'
A commodity is priced by its demand. If you took currency out of the discussion, than a commodity is worth whatever it is worth to you. When currency is considered, than the value is determined by what others are willing to pay.
You cannot read the future, but only estimate what something will be worth (player). That player may never play a game for you. Their 'worth' though, was what you paid at time of 'purchase'. Hindsight may determine that you paid too much or little, weighed up against other players of similarly considered value.
Disassembling, in my opinion.
That is a different kind of 'worth'. We are talking about players. Teams all need players. Yes, a specific midfielder may be 'worth' more than a KPP to a specific team at a certain point in it's development. But that midfielder is still valued (at time of 'purchase') by the market.
I'm not defining anything - the language does.
There are many ways to look at 'worth' and 'value' - not just relatively, but also comparatively, in hindsight, complimentarily, and of course, when dealing with people - what the player wants themselves makes a difference to the 'worth'.
All said - this isn't, in my opinion, a point that was really worth arguing.