From xonar's answers I estimate the value of a bitcoin to be about 8 €. This is the value xonar produces. Assuming that he is among the less productive miners with a small capital we may assume that the real value is a few € lower, maybe 4 € to 6 € or $5.5 to $8.5. The difference between value and price of $15 to $25 can thus be attributed to speculation.

I don't doubt this. It's interesting what to operate at a loss means in the Bitcoin economy. It seems quite difficult to make a loss when there's a strong deflation. Even if you don't operate at all, you certainly make a profit. Of course, there's still the final crash, which will produce a few winners and and an army of losers.

Almost right. The price tends to or fluctuates around the value. Value is not equal to cost. Roughly, value is cost plus surplus value.

Never said such things. I acknowledge that the price is not the value. That's obvious when one takes a look at the charts. But I'm interested in what the value is. The big price fluctuations can be explained with speculation.

By looking at the price nobody will find anything about value. You need to look at the composition of the mining capital.

To assess the value of a bitcoin according to Marxian economics I ask miners to answer a few questions. We all may find out from the answers how the price of a bitcoin relates to its value. I also hope to convince some of those followers of vulgar economy (as Marx called it) that their contradicting theories of value are wrong. It's important that only miners answer. I regard as a miner a person who has at least some graphic cards running 24/7 to mine bitcoins and who has been mining for at least 6 months. My questions:

1. What did your mining hardware which you are currently using cost?
2. How much did you pay last month for electricity only for mining bitcoins?
3. How many bitcoins did you mine last month?
4. After what period of usage did you replace your mining hardware or, if you have not, when do you intend to replace it?
5. How much did you pay as wages last month? (If you work alone: How much of your income from bitcoins did you keep for yourself, how much did you invest in your mining business or save to invest it?)
6. How much did you pay last month for rent? (the rent for the rooms where your mining hardware is located)

Thank you for your participation. Soon we'll see clearly what the real value of a bitcoin is.

Very good point. Few people see this problem. It is absolutely necessary that money can be created at no cost whenever it is needed. If this is not possible, production can not be extended. Normally, money is created by credit. Bitcoin doesn't have this possibility. Whatever it is, it's not a functional currency.

I wonder how Satoshi came up with his magical number of 19% deflation p.a. Did he study some secret economics to arrive at his absurd "insight"? I guess he just set this value because he thought 19% would be a nice annual increase of his fortune.

alexk, I think the monetary system you are looking for, which has not the flaws of Bitcoin, already exists. What do you think of the Ripple project?