> They would certainly not be cheap, because they are relatively more expensive due to the extra depreciation cost.
This depends on how long you expect to keep money on a side chain and how many transactions you plan on doing. Inflation is a great way of paying PoS / PoB miners - that cannot introduce issues with consolidation. If you design the inflation schedule correctly, it should be balance transaction costs *precisely*. Indeed, you can calculate the exact amount of inflation needed to guarantee that a side chain is always exactly 10 times cheaper than bitcoin.
>As I posted to bitcoin-discuss last week, I support UTXO commitments for sidechains.
Indeed, I think side chain nodes should always be fast-synced from 6 month old commitments and thus be ephemeral, cheap, and never appropriate for long term storage. This would provide the best possible incentive structure to keep the main chain secure, paid for with high clearing fees, etc.
> I don't think that blind merged mining messes with the main chain's incentive structure
The critical issue is that we cannot introduce protocol changes that further incentivize geographical and institutional consolidation. Miners who are able to deal with the bandwidth caused by drivechain coffee transactions will profit from these transactions, whereas smaller and more geographically distributed miners will not. Those miners will, in turn, build faster ASICs and buy more electricity and drive out smaller players. I think this is abundantly clear, and is the primary motivation behind preserving block size limits.
If this premise is false (which it may be), or is skewed so as to damage bitcoin as a whole (could be as well), then that needs to be demonstrated first.
The lightning model does the opposite of this. Miners watch fees increase and coming from an *orthoganal* protocol that cannot cause further centralization.
One problem is that the main chain also *must* grow in response to bandwidth, or the disadvantages of using the main chain will weaken financial support and hashrate securing it. I believe this is also true, and that a "balancing act" will be Bitcoin's norm until we adopt something like BIP103 - which provides a steady and appropriate growth.