Nothing wrong with putting a price on something you put hard work into. Honestly I think the $5 price tag is perfect. It's not too much so it shouldn't put many people off from purchasing, and it's not too little so you should get a decent return if your downloads are going up.
This is from a consumer standpoint though, so take my words with a grain of salt. I haven't actually developed anything worth putting a price tag on yet haha. Game seems solid though, and is very unique. Keep at it my man, you're killing it.