I got it, in your scenario the #dollar become shit and #Bitcoin will shoot up. The main chain fees will be over the roof and people will prefer #LN. But, it doesn't mean, LN sats will be more expensive. Like I'm not going to swap ALL my corn from on-chain, most people won't. We will earn and use LN and #Liquid sats, while treat on-chain as a savings account.
Let's say I earn/save up 1 #BTC on LN. Now, the on-chain BTC costs only 0.8 BTC. What will I do? Buy that shit straight away. The price will get to the same level because most of people will be willing to do so.
For large quantities like 1 whole bitcoin sure. As the price of Bitcoin rises to the moon, the threshold for the size of the quantity you'd want to do that with will increase. This would price the average user out, who has never touched 1 full BTC, and make it predominately market makers who'd charge a premium above pure conversion cost.
Therefore, we argue that investing in Lightning now, at the same price as on-chain to arbitrage it is low risk with a decent chance at payoff.