Before thinking of the price that would be required, think of the first part mentioned, transactions cost would have to be ~$125k, if we take the last full block, 754925 has 1,492 transactions, so that would be around 83$ per tx, who do you think is going to pay that amount?
It's just a hypothesis and would not be fully put to the test until a while in the future. The perspective of LN taking many of the transactions off chain and only needing to open or close channels on chain, increasing the fees of such individual transactions. The downside is such a situation would practically force everyone to go for off chain means of transacting as, no one would spend ridiculous amount on a single transaction.