Actually, the sticker ecommerce site was completed some time ago for the original series. (bingies.com)

As to the cost, it is not unusual for similar sized / quality stickers to retail for $4.99 on Amazon and other sites. Selling stickers comes with lots of hidden costs most don't recognize, which only become trivial when you sell them by the tens of thousands. Ours seem rather reasonably priced compared to current market trends. Sure, you can find random stickers for less, but you could pay quite a bit more as well.