There's no fixed formula, but these habits help your price feel fair to a buyer scrolling past dozens of other listings.
Search Browse for the same title, or similar books in the same category and condition, before you set a price. Buyers compare listings side by side, so pricing far above the going rate mostly gets you skipped.
A Fair-condition copy priced like a Like New one will sit unsold. Let your own condition grade — not the original cover price — anchor what you ask.
Prices like 450 or 500 read as considered; a price like 437 reads as arbitrary. Small rounding doesn't cost you much and makes the listing easier to scan.
Many buyers will ask for a small discount, especially in person. Pricing with a little headroom means you can say yes without feeling like you're taking a loss.
If a book has sat listed for a while, grouping it with others into a bundle at a combined price can move it faster than waiting for a buyer who wants that exact title alone.