For paperbacks, the royalties vary by country, but in the U.S. it's a little over $3. For Kindle, it's about $3.50.
And by the way, the numbers I gave you earlier are for both books together, not just one.
I use the Amazon tool that estimates what price is best for selling a book. Pricing is an interesting thing: if you are too low or too high, your sales are affected. Too high and of course you discourage people, but too low and the perception can be it has little value and thus ignored. For Kindle unlimited, since people can read unlimited books for one price, they often skip cheap or free books because they want to get a "value" for their monthly subscription. So, you have to find the right prices for both printed and digital book formats in order to get the most sales.
For me, sales means eyes, ears and ultimately, hearts.