Players that play in a high salary league and then sign a free agent contract with a low salary league seem to ignore the financial rules set for the new league.
In the example provided, Omar Serrino went from the MLB (a high salary league) to the Puerto Rico League (a low salary league) during free agency. Serrino signed a 7 year, 88 million dollar contract. The Puerto Rico League is setup to only allow Superstar players to make 2 million a year. The game seems to ignore the financial rules set for the league he is signing with and instead used the financial rules for the league he left. Here are some screen shots:
Here are the financial rules for the Puerto Rico League:
Here is the financial report for the Puerto Rico League, notice how at least 4 players are making way over the Super Star Quality Player typical salary.
Here is a screen shot of the highest paid player, Omar Serrino, who signed the 7 year, $88 million deal on 11-22-2064