The later you speak of, when there would be no more block reward is over 100 years from now; a lot would have happened between that period of time which would change the Bitcoin space from what it is now.
I specifically didn’t write any btc amounts in the calculation only dollar amounts. Since miners will pay their ASICS and electricity in dollar. That the value that matters.
Since transaction fees are paid in Bitcoin, it would be best to describe it in that form.
If 0.000030
BTC equals to just over a dollar now, it would be a lot different in price in 2140 (expected time of the last block reward).