Fluctuating player values (pre-season)

Does anyone know why player values fluctuate so wildly pre-season?

I'm mainly talking about players who I transfer list right at the beginning of the game. I always set the asking price at half the player value. Then, when I check back a couple of days later after a wanted sign comes up, and their value has gone up dramatically?

Obviously I understand why a player's value would go up during the season after good performances or down if they weren't playing, but what makes this happen when no games are being played? It makes it hard to set a realistic asking price, and it doesn't seem to happen to transfer-listed players at other clubs?

when players are wanted by many clubs the value goes up. Same with anything in life really. If the demand exceeds the supply the value rises. The supply is one player and the clubs intrested feel they have competition for the player then what they are willing to pay more to get their player than if it was just them bidding for the player on their own, this increases their value.

Just my view

It's not just the players who have lots of interest in them though, it seems to be totally random?

It also doesn't explain why players at other clubs values don't seem to rise in a similar way?

I've had players values decrease overnight, which may or may not be down to several occasions of not getting any offers for the player at the moderately high price I've asked for in a short space of time.