1. The author points out that txn fees are tiny, 1% of the revenue. And they are unlikely to be significant during the depreciation period of the machines.

2/3. Sure, but see #1.

4. Sure, but the author is pointing out that the cost of buying BTC exposure via these companies is higher than just buying BTC by a lot. It almost seems like a short position of these companies combined with a long position on BTC is a solid bet over a long term horizon.