Micro-payments have come to the Internet. Just not through credit cards. Look at any "Free2Play" online game and you can find plenty of micro-payment variants.

For a non-game implementation, look at Amazon coins. Once you overcome the transactional costs of traditional methods, it's very cheap - fractions of a cent to process. The only efficiency problem with private currencies is the breakage around conversion - usually you can't buy "just one", and if you don't use up all the converted private currency, you strand that value in the economy that uses that private currency. So it only really works for ecosystems that are "large enough".

BTW, I agree with everything else you said. Content providers have an inflated sense of their content's worth, and need to reset their pricing models.

Something like GDG would have been anathema to the original file system creators of Unix - at least through the Berkeley FFS days. I think I saw something like it on some extensions in 4.1ES. It was certainly on VMS. Maybe something like ext3cow will do what you are thinking of. Of course much of the problem is that Unix at the mothership was used extensively to submit JCL to OS/360 hosts, so all that stuff was done back on the big iron, not the cheap Unix FEs. Departments had to cough up for the unix hosts but projects paid for time on big iron. I never worked on projects that cared about that - network design not legacy OSS dev.