Scaling? Yes, towards thousands, ehm, hundred thou.., ehmm, Billions! We have tested our current commit-chain implementation with up to 100'000 client accounts, and the costs grow such that one commit-chain can support more than 1 Billion users 😊 - no matter how many transactions are done on the commit-chain.
Moreover, clients are light by nature and have only a few kb of storage and bandwidth requirements. Note, however, that clients are required to come online once in a round (every 36h) to audit their state. We plan to relax this requirements with watchtowers.
Now, please enjoy the following graph that shows on the x-axis up to 1 Billion users, and on the y-axis the blockchain costs for withdrawal (exit) and disputes with the operator.
More detailed and finer granular cost analysis can be found in the following table.