I'll just pinch in a little bit to clarify some details and then re-close.
1. "Normal" teams (as opposed to day traders) with a low number of past transfers can actually sell their whole teams at a pretty high percentage. The percentage actually drops only after a successful sale. So you could have sold 15 players at almost max percentage, you just have to list them all at the same time and with a low enough starting price (risky!).
2. The percentage of the money received is recorded at the time of the transfer listing, not at the time of sale. This means that the percentage received is always the one shown when the player was listed.
Just wanted to clear that up.