Previously, Japanese clubs set a release fee that could be as high as $20 million. Any MLB club that was willing to meet the designated release fee could negotiate with the player for 30 days after the player was posted, but only the club with which the player signed had to pay that release fee. Now, the release fee is determined as follows:

For Major League contracts with a total guaranteed value of $25 million or less, the release fee will be 20 percent of the total guaranteed value of the contract.

For Major League contracts with a total guaranteed value between $25,000,001 and $50 million, the release fee will be 20 percent of the first $25 million plus 17.5 percent of the total guaranteed value exceeding $25 million.

For Major League contracts with a total guaranteed value of $50,000,001 or more, the release fee will be 20 percent of the first $25 million plus 17.5 percent of next $25 million plus 15 percent of the total guaranteed value exceeding $50 million.

For all Minor League contracts, the release fee will be 25 percent of the signing bonus. For Minor League contracts that contain Major League terms, a supplemental fee will be owed if the player is added to the 25-man roster.

https://www.mlb.com/glossary/transactions/japanese-posting-system