It's a slow day at work, so I just had a wee look at this. Usual caveat that this is based on five minutes Googling and some fag-packet arithmetic, not any Skyline Drifter style working knowledge.
Every time a player is transferred between countries for a fee, 5% of the fee is held back and allocated to the clubs who helped develop the player (regardless of the player's current age).
So if we take the reported €500,000 as gospel, €25,000 would be held back. It's then divided proportionately between any clubs that the player spent time at between their 12th and 23rd birthdays.
I don't know how loan periods affect it, but Bates didn't leave us permanently for Rangers until shortly after his 20th birthday. I've no idea if he was at a boys club before joining the Rovers youth set up and when that might've changed, but if we assume for argument's sake that he was with the club from the age of 12, we'd be looking at something like €16,000 or £13,500. Even if he didn't join until he was 16 it'd still be about €9,000.
Not the worst news in a week where we could do with some cheering up!