The Heat guard was assessed a technical foul and ejected from the game when he tossed his shoe midway through the fourth quarter.
"I'm just learning from it and going forward," Richardson said Monday before his fine was announced.
On Sunday, Richardson described his actions as the result of "a series of events."
"I got caught up. I wasn't really thinking about much," he said. "I was thinking about how frustrated I was. And going forward I can't let that happen."
With 6:40 remaining in the fourth quarter, Richardson drove for a dunk and felt he was fouled by the Lakers' Josh Hart. As Richardson hit the floor underneath the Heat basket, his left shoe came loose. Richardson took it off and flicked it initially right in front of him. Upset, Richardson showed his shoe to official Kevin Scott.
As play resumed, Richardson's frustration mounted. He drew his fifth personal foul and also threw his shoe against the scorer's table. When Miami coach Erik Spoelstra motioned for Richardson to head to the bench, Richardson flung his shoe far into the stands. Scott whistled Richardson for a technical before ejecting him from the game.
This was Richardson's first career ejection in his four seasons, according to ESPN Stats & Info.
"You saw a competitive will come out," Spoelstra said. "I think probably what you saw more than anything, and I agree with Josh -- not throwing his shoe into the stands, that's unacceptable -- but going in for the dunk when there's some contact there and he lost his shoe. ... From my angle it looked like there was contact."
Seconds later, Spoelstra was given a technical foul by officials as well.
ESPN's Ohm Youngmisuk contributed to this report.