Absolutely not. They're actually very inexpensive. I'm pretty new, so I'm not sure how all these things work, but I've actually heard that pricing your items too low can have a negative impact on your sales because people might assume they are cheaply made, which your products aren't. However, I was looking at your shipping prices and they seem a little high, but that might just be because you are in the UK. Still, maybe you could try raising your prices and lowering your shipping? Just a thought, I'm not sure if it would really help or not.
I love your stuff though! Potter lovers unite!!!