It's not unrealistic real teams tank in real life if it benefits the club, Teams tank for draft picks all the time.
but far away from these extrems, and what i have seen from the NBA they don't forfeit their game even now when the Po are unreachable for most.
And at least in our top divison most of the team who try stay into the devision, and i don't want to make team who get demoted run economical bad. But in your example, with the low transfer sumd you get the salry from 300 to 400 k, and still make 200k each week. Which is more sympathic for me then, promote and reduce the salary to 30k and make 550k each week.