No no no no no NO!
The player depreciation is definitely
a bug. It was supposed to be ironed out with numerous updates on magazine cover disks (plus the original SWOS v1.1 update disk) but it was never really fixed. It's really annoying when you're star player and league top scorer drops by £5m.
The only players who really seem to increase in value are the reserve and trial players. If you get a good one keep playing him and his value can soar to over £1 million!
The reserve players are random in their skills so you never know how much they are really worth until you keep playing them. A big tick when you include them in the first team is usually a good indicator of how valuable a player is.
A few months ago I was playing a career with Real Madrid. I got a Midfield reserve player called Savo Zalazar. I couldn't believe it when he eventually peaked at an incredible £12 million!!
Amazing but very true. That's only happened to me once (and I've been playing SWOS for over 7 years) so it's very very rare.