September 21st is when the border is "scheduled" to take waiver applications. This is an important date because on October 2, the waiver fee is scheduled to increase to $1400 from $585USD.
As I mentioned below, you could be pay the lower fee on eSAFE (presumably on October 1) and hope that they either extend the time the fee is applicable or that the border opens before November 15th, when the 45 day window would expire.**
**When you pay over eSafe you have 45 days to go to the border and do your fingerprints, or the application is considered abandoned**
Let us just hope that the border opens September 21st.