I'll make an extreme example: Someone could put hours and hours into building a black-and-white TV. Is anyone going to buy that? It reminds of the "Labor theory of value" https://en.wikipedia.org/wiki/Labor_theory_of_value
The interesting thing is, that I could argue, that the money I have to invest is the expression of previously done labor, which actually found someone who wanted to pay for it.
Back to Steemit: "value" is subjective (hence "Subjective Proof of Work Algorithm"). If you are here one month, you've noticed the rewards diminishing. Why is that? Has your work become less valuable? No. It's the Steem price that has declined. Why? Because there are not many incentives to put "former work" (=money in the form of BTC) into it. Will that trend change? Maybe, but that's exactly why I wrote this article, because the incentives are low right now.
You are right (imho) when it comes the subjectivity of the "value" of currencies. There is no real reason why Gold is more expensive than Platinum, other than the tacid agreement of "the market" that Gold is Money and Platinum is an industrial commodity. Maybe that could change and the World Platinum Council has been working marketingwise for years to make it at least be considere "jewelry" (with decent success). As for Gold: nobody (imho) can give a reasonable answer of where the price in USD should be. I always say, that I'm only very confident it will stay more expensive than dust, as it did in the last 4000 years (it might not sound very sexy, but you`ll have a hard time finding any particular (!) asset that can say that. You might say "stocks", but which one? The Dow Jones of today has nothing to do with the one started. Most of the companies in the original Dow are dead, so it's misleading).
Now enters Steem, which is designed more like Copper (not scarce, easy to find etc). So you need heavy incentives to actually find people to buy Steem with USD or BTC or whatever. Only that gives Steem the price I talked about earlier and that is the "value" you see below your posts.
Bitcoin has an easy "story" to sell: digital Gold. It took quite a while, but now we might have a couple of million people in the world believing it will stay more expensive than dust. You don't have that with Steem (which is backing SP and SBD!!!). Speculators only buy copper if they think someone will need it for whatever copper is needed for in the future. So what will people NEED Steem for in the future? There are possible answers. But the point of my article is precisely to point to the fact, that imho this aspect is underdiscussed and this whole discussion of the article actually proves my point, because I have yet to get an answer.
I hope that made sense (and again, sorry for my english, no native speaker).

PS: What are all the comments I made here "worth"? Is it "valuable" that I ask questions I consider crucial for the survival of the network, even when in general people don't really like to think about it and instead prefer hoping? I don't know. But I don't get what I'm used to get when I do financial consulting. Still, it was a lot of "work".