It's an ATH for the market cap, because although the price is lower than April, the total number of coins is higher. It's easy to forget that the annual bitcoin inflation rate is still running at over 12% !!
So btc is undervalued in your opinion?
I think the potential upside is at least 1 to 2 orders of magnitude higher than the current price in the medium term (2-5 years).
Against that, there are risks (Regulation, technical failure, lack of adoption, exchange failures etc). But network effects are so powerful that it is hard to see any show-stoppers.