Actually the problem is when you buying a 250k salary player for 10k, play him on 2-3 games then fire him just before salary.
Rookie salary is not a big amount. When you go bankrupt, you don't buy 250k salary guys.
Anyway, the rule could be this: you can't fire a player who played a game on your team, before giving him a week of salary.
This way, rookie salary doesn't count as they didn't play a single minute for you. When you sell a player who was part of team for weeks, months, years, the rule doesn't affect you, because you already paid a week of salary earlier. The only case that this rule counts is the case mentioned in the top row.
Don't feed the troll