US Embassy in China Weibo Reminder!
Department of Homeland Security: If you are unlawfully present in the United States, leave immediately and use the CBP Home application to self-deport. If you do not do so, you will face consequences. One of the consequences is: staying beyond the final order of removal deadline, with a penalty of nearly $1000 for each day of overstay.
Specifically, the penalty for overstaying is $988 per day.
$988 may not be much for the wealthy, but it is indeed a significant amount for an undocumented immigrant. If you cannot pay, even stricter penalties await.