Correct me if Im wrong!
You're correct. Bitcoin, though, will always be profitable for some. It's just that the security of the network will decrease overtime.
You are wrong and since you like to use USD values I'll give you USD values.
When bitcoin started miners were earning $0 per block. We fast forward to each time the money they earned was cut in half (dropped 50%):
- 2012-11-28 they were earning $75 per block
- 2016-07-09 they were earning $8,500 per block
- 2020-05-11 they were earning $61,875 per block
- 2021-03-09 they are earning $309,525 per block
All the above values are with 0 fees per block!
But, Bitcoin didn't worth the same all these years. It's a false thought to compare 2012 with 2016 and then with 2020, 2021, unless you think that one Bitcoin will worth a billion dollars when the reward shrinks by a lot. If the price isn't doubling each halving, then the security will decrease.
Besides, OP didn't refer to the previous rewards, but when there won't be a reward.