Too long and i dont think anyone will read beyond the first point.

Anyway, no one in the forum ever implied that Market Value vs Salary equation determines the better player. It determines fast trainers/potential. Fast trainers are not guaranteed performers.

Based on your breakdown...

Player A is 26 skill, $1.9m in value and on a $2.3k salary
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Player B is 25 skill, $1.8m in value and on a $12.5k salary.

I would buy Player A because he would train faster, assuming both are < 22 years old.

As a player age, his value does not necessarily drop because his rise in quality.

Also, I think it is unnecessary for you to spend so much time analyzing an FB/mobile game as the game engine is not like FM. It is much simpler and you just need to have fun!