[david-given]

Does anyone have any information about Ethereum costing?

That is, on an average machine, how long does it take to mine a block, and how much processing/storage do we get with that block? Do we need to mine a complete block before we can get any work done?

My concern is that if I want to build an app with a simple message bus and a small amount of transactional state, each client might need to mine for a prohibitive amount of time before it can actually start participating in the network.

[barnabee]

I am not sure regarding the block times, but for connecting clients for the purpose of running a simple app, you may be interested in the light client protocol, which according to the link below only requires processing of ~1kb of network data every 2 mins.

https://github.com/ethereum/wiki/wiki/Light-client-protocol