Hmm... well it's only showing a button for $5. I'm happy to add $5 (to make it $10) when I purchase it, I just wanted to make sure I got the updated version and you get what you should.
So even with my previous purchase, when I click the Buy Now button, the only way I can get the Expanded edition is to pay $15. But Itch is definitely showing I own the old version (you can see it in the background).