Optimal price points depend to some extent on how much prospective readers will pay. Price it as high as the market will bear--but that requires experimentation.
Long ago, I learned that big trad bestsellers are not a good benchmark for indies. A better one would be what typical indies in our genre are doing. The best one would be to learn by experimenting what price point works best for us.
The notion that $.99 promos are not a good use of our marketing budget raised the related question of what is. I still do newsletter promos occasionally, mostly for new releases, and they mostly cost more than I make, but they do at least keep the new book from sinking immediately into the abyss. What the long-term effects are is harder to judge.
Neither FB ads nor BookBub ads ever did much for me (I mean the ads, not the promos, which I've never gotten.) AMS ads used to, but they've gotten progressively less profitable. That said, Anarchist has inspired me to monitor more closely and see if I can wring profit out of them.
In that regard, I have an observation which probably isn't worth starting a new thread for, so I'll mention it here. In looking at the kind of searches that fall under broad use of keywords, I was shocked to discover that some of them are irrelevant to my books. One of the search terms that customers were using fairly often (but that never produced any sales) was "stuff your Kindle free books." (I'm not kidding!) None of my books are free, so any clicks I got from that would be useless. Similarly, author searches for people I've never heard of came out of broad use of fantasy. All of those clicks went down the drain, too. I use some authors as keywords, but very carefully, usually people with whom I have something in common beyond just genre. Some of those actually produce sales. But random fantasy authors don't seem to. I also got clicks from m/m fantasy (broad result growing out of fantasy again). None of my books so far have m/m relationships, so again, the clicks went down the drain.
I'm experimenting using only exact and phrase categories. No more broad! My impressions are accumulating slowly, but at least I'm not getting buried in fruitless clicks right away. If that comes to anything, I'll start a thread for it.
I'm also trying a new feature of the sponsored brand ads. I knew they now required a non-book-cover image. What I didn't know was that you could have up to five (which then become a slide show). It's probably not as effective as video, which you can also do, but it's less labor-intensive to create, and our eyes do tend to be drawn to movement. Anyway, I set up four ads (one linking to the author page, the other three to specially made pages to emphasize a series). Amazon should allow linking to the already-existing series page as an option, but so far it doesn't. All four have slide shows. If those are more effective, I should see a difference between my first batch of image sponsored brand ads (which I've now turned off), and my current ones.
Beyond that, I'm monitoring frequently to see if I can find any patterns. I'm to the point where I'd see even a slightly less negative ROI as progress.