Ok good. We have established it to be a non-trivial cost.
Now, what is the growth complexity of the total cost of the network in
terms of number of connections each hub has to other hubs? And then,
consider a payment channel with many hops in it. The end-to-end users would
have to swallow all the costs of the hubs in the channel.

On 9 August 2015 at 22:57, Patrick Strateman via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> The costs of operating a hub are as follows:
>
> Time value of the funds the Hub has locked up in payment channels.
> Enhanced risk of loss of control of private keys (the keys necessarily
> need to be on an internet connected system).
> Operating costs (I expect this will be minimal).
>
> The hub can charge a fee for it's services to recoup these costs.
>
>
> On 08/09/2015 02:45 PM, Hector Chu via bitcoin-dev wrote:
>
> Tom, my understanding is that the money that is debited from a payment hub
> is simultaneously credited from either another payment hub or the person
> making the payment, so that the net funds flow at a payment hub always sums
> to zero. So no, there is no credit advanced by the payment hub to anyone.
>
> Given Mark's previous answer of using CPFP and other tricks to pay for the
> Bitcoin transaction fees, we can assume that Bitcoin fees do not play a
> part in the payment channel balances.
>
> So, the interesting question is what are the costs of running a payment
> hub? The tx fees that a payment hub would have to pay to settle its Bitcoin
> transactions would be passed on as a cost to the clients of the payment
> hub. Also there is a cost to locking up funds in a payment channel (time
> value of money). The lost interest or opportunity cost on those funds would
> need to be paid for by its clients as well. And don't forget normal running
> costs such as networking and electricity.
>
> On 9 August 2015 at 22:27, Tom Harding via bitcoin-dev <
> bitcoin-dev@lists.linuxfoundation.org> wrote:
>
>> On Aug 9, 2015 11:54 AM, "Mark Friedenbach" <mark@friedenbach.org> wrote:
>>
>> > On the contrary the funds were advanced by the hub on the creation of
>> the channel. There is no credit involved.
>>
>> That's a chuckle.
>>
>> As I said, nothing requires the hub to advance anything, and if it does,
>> Bob can expect to pay for it.
>>
>> We'll see whether hubs assess a fee for depositing funds, whether the fee
>> depends on the amount deposited, and whether it depends on the amount of
>> time it stays there.
>>
>> I predict "all of the above." There is a name for these kinds of fees.
>> Can you guess it?
>>
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>>
>>
>
>
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