Start off by following the headline link, check out the graph at the top of the article, showing quarterly iPod and wearable revenues. In 2007, Q4, iPod revenue hit a historic high of about $4 billion. Now read on.

Horace Dediu, Asymco:

My [Apple] Watch revenue estimate was $4.2 billion in the fourth quarter of 2018. This conclusion was confirmed by statements from the Company.

And:

Looking forward to the next quarter, I am expecting a 51% increase y/y for Wearables and 24% growth in Watch. This results in a Watch revenues about $5.2 billion and non-Watch $5.7 billion. Now if we assume $1.7 billion for non-Watch-non-AirPods (i.e. Apple TV, HomePod, Beats, iPod, other) then this quarter AirPods will have overtaken peak iPod.

Apple Watch and AirPods have both reached historic levels for Apple. I suspect AirPods will be the new benchmark to which all future products will be compared.