you set the price way too low on a transfer listed player. when you get a bid you ask for a trade with the highest valued player they have. they probably won't accept it since trades almost never go through in the game, and they offer you what the player is worth instead.
maybe he's not the same but i have brzailian alex in arsenal, in 05-06 season, aged about 28-29, and i've sold him for 42m.
bought in 02-03 for 22m. he was 26 then.
and check aoun you swede leandersson. when he was 17 he won every player of the month awards except one in german 2nd division, then i scouts insisted that would buy him, i did and few years later he was worth more than 20 million. though in my another game he sucked and never got away from mjallby...