In this specific case, it's about a bloke who was ridiculing...

In this specific case, it's about a bloke who was ridiculing others for buying at "the top", when in fact he was making purchases right up there too (in fact his purchase was pretty much the absolute peak for the following 4 years). It's a playful way to highlight hypocrisy with a touch of history. On a broader scale, it's amusing to point out how certain individuals have been echoing the same sentiments for years, shedding light on the accuracy of their current commentary.

If someone dishes out ridicule, they should expect some in return, often with a nostalgic twist. Of course, not everyone finds it funny and that's okay—humour varies from person to person.