Thanks for the great response. The link about P2TR is something to chew on for sure.
However, these kinds of scenarios always strikes me as remarkably modest, given that actual btc use by real people (vs rabid bitcoiners or speculators) is extremely low, which I calibrate by the fact that my IRL normie friends outnumber my btc friends 30-1 at least, and even my btc friends transact in btc a fraction as often as they transact in fiat. So if btc succeeds by any realistic definition of the word success, it seems inevitable that there would be 10x the actual on-chain transacting, which we could estimate with shorthand as 10x fees.
In practice, rising fee pressure would really kick L2/L3 adoption in the ass; and maybe people would just keep their corn on exchanges; and maybe fee rates escalating that high would short-circuit the adoption process s.t. it strangled adoption in the crib. The system is dynamic and complicated, I understand that. But even so, under the "success" scenario, 300 sat / vbyte seems absurdly low to me.
What's your take to that take?