I really don't understand why people (and media as well) keep saying that BTC reached a new ATH. According to CoinMarketCap, BTC's ATH was at
20.089$ and this event happened on December 17th, 2017.
What happened recently, on December 1st, was BTC reaching a value very cloae to its ATH, but not a new ATH.
I am not sure what happened exactly on that day (even I was in the market) and why coinmarketcap gives us the 2017 all time high at $20.089. I recalled I have never seen bitcoin broke $20,000 in 2017. Double check with price charts on Trading view, it seems data from CMC is wrong on 2017 All time high.
You are right about that price from CMC (I used their price table for my analysis so I knew it).