Interesting - I know Pieter Levels has sold a lot of his ebook at $30 as well which is a lot more than your average ebook. He even started selling before he had started writing it, haha
I imagine he had an intuitive grasp of elasticity of demand.
From what I know his audience is quite "hardcore", and there is hardly many substitute "Indie Hacker esque" stories out there.
I think it's odd how simply changing the format of your product, i.e. eBook, online course, webinar etc ... has such a bearing on the price you can charge.