On: How many Bitcoins does it cost to maintain the Bit...

[api]

The real question is: how much does it really cost to clear a transaction? And how much of that cost is being hidden via being subsidized through a speculative mining frenzy? What happens to real-world TX costs when mining isn't a hot thing anymore?

[icebraining → api]

The real question is: how much does it really cost to clear a transaction?

Anywhere from a fraction of a cent to millions of dollars. Bitcoin transactions don't have a fixed cost, it depends on how many people are mining. More miners => increased difficult => higher costs.

[gfody → icebraining]

There is an intrinsic cost associated with hashing and rehashing the blockchain to secure the transaction. In terms of cpu time, electricity, etc.

[icebraining → gfody]

Yes, but if there were no more miners, you could process all transactions on a single cheap laptop, which probably costs less than $1/day to run.

[akira2501 → icebraining]

So, what happens when they hit 21m bitcoin and mining no longer offers a reward?

[wmf → akira2501]

Everybody sells their now-worthless miners for scrap and the difficulty falls to a reasonable level.

[wmf → api]

how much does it really cost to clear a transaction?

One way to look at that is (25 BTC / block) / (# of transactions / block). About 60 mBTC/transaction given https://blockchain.info/charts/n-transactions-per-block

Fortunately the transaction itself does not have to pay for its own processing.