If you need 1.000.000 xlm for a few seconds quite often, don’t you think parties will want to have a supply before buying?

I think they will start to hold a supply to be sure to have enough when they need it AND have control over the price they buy them for. I think the 4,5 seconds theory is flawed for not taking this into concideration.

Also, I think the minimum amount of lumens per account will start to have an influence when the network is adopted. To fully serve a few million people might need 100 millions of public keys.