Using my AMEX Platinum Personal card:
8/9 - Purchased a flight for $103.98
8/9 - Purchased a flight for $103.98 (A seperate purchase/same flight)
8/12 - Meter moved to 0
No credit applied yet. All of the uncertainty of exactly what the sweet spot is, but I think my $103.98 pucrhase is the highest I have seen to move the meter or get credited.
Will update when I get credited!