When you offer a player to AI teams then it means that no one of AI teams needs this player at the moment otherwise they would come to you with an offer for him so in this case the best what you can get is very small amount of transfer money, usually, it's 3 or 5 times less than the "real" value of the player.
But when AI teams come to you with offer for some of your players then it means they desperately want him and in this case you can get 3 or 5 more money for him than his "real" value...
It's the same principles as we see in real life when it comes to trading
I never offer my players, it's the worst way to get a fee. I don't always get such great value, but these players I sold the clubs kept bidding so the price kept going up. I think Madrid bid about 30 times for Martial 10 of those were on deadline day, which is when you can really drive up the price.
thanks guys. very helpful