We may never be able to purchase
BTC for less than 5 digits again, ever. You heard it here, first.
#nohomoFurthermore, I am not even clear if the various (perhaps 5-ish clusters, give or take 1 cluster) short-term sinkenings below 5 digits between 9/3 and 9/8 would have counted as sub 5 digits, since the BTC price never did close any daily candle below 5 digits.
In other words, if no daily candle closed below 5 digits, did below 5 digits even happen? #justasking

I'd go by daily candle closes, which implies that a true trading opportunity has arrived. Taken to the other extreme, if a single satoshi trades under 5 digits, would that count? I'd argue no, flash drops like that can be considered insignificant noise.