I honestly don't think the average person thought much about the cost of buying legislation. Even today, I think the average person feels intimidated by legislation and doesn't want to read it even if it is all freely available.
As far as the official version of federal/national legislation goes – in 1947, in both the US and the UK, that was sold by a government agency overall at cost or even at a loss. ("Overall at cost" meaning, they might sometimes have made a profit on an individual print run, but profits they made on some print runs were balanced by losses on others, so they didn't make a profit overall.)
However, most lawyers preferred to use private editions published by for-profit publishers, which added copyrighted notes providing cross-references to other relevant legislation, important court decisions, etc. So the "raw" version of the legislation was available at-cost but the version most lawyers actually used was not. And that remains true today – most lawyers don't rely on the freely available versions on the web, they use expensive commercial subscription services (Westlaw, LexisNexis, etc) which add lots of very useful privately copyrighted notes–and you really need the information in those notes to properly interpret the law, because if you don't have cross-references to other legislation and case law, you won't know what it really means in practice–and although you could probably reconstruct those notes yourself to some extent (such as by searching free case law databases for references to a certain section of legislation), doing so is laborious and likely to be error-prone (it is easy to miss something important because you didn't use the exactly right search term, etc). So even now, access to the law is not as "free" as many think it is.
> I don't know how much "at cost" would be for ISO, but something tells me it wouldn't be an identical 158 CHF for both PDF and paper.
I think from ISO's viewpoint, it is "at cost", because they are not just including the cost of printing or hosting the download, but also the administrative and editorial costs of producing the underlying standard. ISO is a not-for-profit body and any profit it makes is reinvested into the standard development process. By contrast, when you buy a copy of an Act/Statute from the government print office, you are not paying for the actual running costs of the Congress/Parliament/etc which produced the legislation – that is paid for through taxation – whereas ISO being a private body can't levy taxes.
That's not to say that ISO has to use their current model. They could make all their standards freely available and try to recover the editorial/administrative costs through some other mechanism – charging membership fees to corporations, government grants, etc. However, while those methods are feasible – other standard bodies use them – I think ISO would respond that they would make ISO more dependent upon and more beholden to corporate and government interests than they currently are. I suppose the critical response to that is that ISO already is quite beholden to corporate and government interests, and it is hard to see how it could get any more beholden, but ISO would not agree with that.