Royalties are paid to the author for each book sold. Some publishers pay royalties that look high because they’re based on “net profit” (this is what’s left over after the publisher takes out his expenses). Since there’s a lot of room to hedge when dealing with net, it’s probably safer to go with a publisher who pays royalties based on list price (the price that the book is supposed to sell for). Even if it sells for less, you still get the same royalty. And even if the publisher’s expenses are high, your royalty doesn’t change.