About market value

[Toxcatl]

- on Auction :
increases every season at low levels
increases every two seasons at mid levels
increases every 4-10 seasons at higher levels

Wrong =/

At the first of last season, i bought 10 players with market value of 111M. After 5 days matches, i checked all the players and 2 midfield got decreases market value to 110M. This season, those 2 midfield got back their market value to 111M, but my 2 defender got decreases market value to 110M.

Sounds like you made a mistake. It seems they weren't 111M, not all of them.

Value depends on: quality, age and talent (hidden parameter that determines how fast the player gets XP). Value doesn't depend on special abilities and amount of positions.

If you need boring details: as you probably know, 1% of quality equals 0.25 points of overall quality. Every 1% increases player's value. Every 4th increase (when overall quality gets 1 full point) is bigger.
Every year in age reduces Value, though I don't know the exact numbers.
Talent is a hidden parameter. But comparing players of the same age and same quality we can guess if a player is FT or not.
On higher levels, where overall quality is really big, it is hard to tell FT from non-FT. On extremely high levels it is impossible to do so: every player of the same age and quality has the same value.