That is a historically inaccurate take. s/retail/distributor/ if it helps. The point is that a software developer would have been very lucky to earn a significant fraction of the retail price. 70%? Not even close. The App Store completely reversed this model.
That said, it's valid to acknowledge this history and still think 30% is too much for distribution overhead in 2020. I do not have an opinion on the latter.
They pointed out that retailers would buy the software up front (at wholesale price), and assume the rest of the risk for "promoting, distributing, and selling" themselves. Thus, the retailer did not "charge developers" for those things[0].
I realize this is a bit pedantic but it's not fair to say the parent has said something "historically inaccurate".
[0] There were special marketing or buyback arrangements in some cases, but what's described above is the default retail model.
That said, it's valid to acknowledge this history and still think 30% is too much for distribution overhead in 2020. I do not have an opinion on the latter.