They go on sale at 10x their salary, up to a maximum of 1 million.
And when their salary is so large, paying 1 million often doesn't make sense.
This rule is just so stupid. BB should have come up with something like make their default price $1000 or something like that. I've seen many ex-NT players die off even though they can still be a backup or a starter for lower league teams because they are 30k a week bigmen and they cost 300k+, and with that price you can get a 50k per week bigman. This is just sooooooooooooooooo stupid.
I think this rule was put in so that players would start retiring from the game. Without it, the market just becomes saturated with more and more quality, high salaried players every season. That was a big reason why the market crashed in season 13-14.
I for one think it was a excellent way to take players out of the game which will hopefully keep the market place more constant. Without it, fast forward 5 seasons and you're going to have a ton of players with $100000+ salaries all in their mid to late 30's.