Cronulla and Manly are weighing up whether to contest breach notices totalling $50,000 after Shane Flanagan and Trent Barrett were stung for last weekend's referee blow ups.
Cronulla's Flanagan was been hit with a breach notice of $30,000 after he labelled the officiating as "disgraceful" in his team's elimination loss to North Queensland on Sunday.
Barrett's fine was $20,000 after he blamed officials for ending Manly's season in their loss to Penrith, and asked them into the sheds to explain their decision to the playing group.
The fines come after NRL chief executive Todd Greenberg told the game to "grow up" in a line-in-the-sand speech against the two coaches.
That view was reiterated by NRL head of football Brian Canavan on Tuesday, who said the comments were "beyond acceptable parameters" and damaged the game during the finals.
"Our message is clear - no matter the significance of the match or the specific circumstances, coaches cannot cross the line," Canavan said.
"The integrity of our match officials and the game needs to be protected."
The fines are the largest against coaches since Roosters mentor Trent Robinson approached referee Ben Cummins last Anzac Day.
They took into account the fact Flanagan also labelled the referees "horrendous" and "awful" in a video sent to club members and published on the Sharks website on Sunday night.
The NRL also insisted on Tuesday that the non-selection of Sunday's two on-field referees, Ashley Klein and Gavin Badger, for this weekend's semi-finals was not a demotion, but rather a result in there being two less games.
Meanwhile Barrett's fine also came after he had received another warning earlier this year for comments made against match officials.
The Sea Eagles said they were considering whether to appeal or attempt to have the fine reduced.
"We will be reviewing the basis upon which the NRL breach notice was issued and will be determining our position on the matter in the coming days," the club said in a statement.
The Sharks also followed a similar sentiment in response on Tuesday.
"Our club will review and take advice on the contents of the breach notice and then make a decision as to our next course of action," a Cronulla' statement read.
Both clubs have until next Tuesday to make a decision on their response.