The current transfer system is bad as it gets. It's unfair and make it difficult to acquire a player when you have 50k players and plus bidding; and fortunately the game is even expanding.
BB developers should introduce a more efficient system.
Here's my suggestion:
The seller must set the player's price once for all at a price he deems acceptable (with BB showing how much comparable players were sold for).
The buyers should meet this price and NEGOTIATE with the player for salary and role on the team, preferrably introducing Salary Cap in each country. It is not hard to do. Just add up each teams Net Income of the previous season and divide it by the number of teams; and each team's salaries above the average income must pay luxury-tax; as much as the NBA.
This step will let BB developers introduce Roles, Salaries, Salary Cap, and make it more enjoyable.
Right now, the game is simple, easy for the person thats willing to wait for 3-4-5 seasons to build a contender. There's no real intelligence involved.
Also as the league gets more "managers", it will be able to increase the Revenues of the league and will make the league stronger and will push up the Salary Cap.
Think about it BB developers.