Economic Model for System Para Collators

A couple small points first…

In general, parachains will work best when the collator-selection mechanism is plausibly unique, i.e. for a parachain block at any given position there are typically not forks. For that reason the ‘free-for-all’ approach is definitely not ideal.

This might be of relevance to Allow "Restaking" of relay-chain stake through custom slashing privileges .

More to the main point…

Materially, it doesn’t seem to me that there is much difference in computing this on the front-end of inflation or on the back-end of the treasury. Couldn’t we also consider alternative models where the treasury votes to send DOT to system parachains, to be distributed as rewards to the collators of those parachains?

The reason I bring this up is that, as you point out, parachain collators don’t provide any service except for liveness & censorship resistance. As such, I believe that the amount of rewards for system parachain collators should be relatively low - 20% of inflation seems quite high to me. Furthermore, since opportunity costs are less of a factor without a need for slashing, it seems to me that the rewards per system chain should be based on the real costs operational nodes for system chains undertake. This will vary heavily from one chain to the next - something like Statemint is extremely lightweight compared to e.g. a storage chain and I think we’d want to give the treasury the ability to budget accordingly.

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