Even with shipping, it was less expensive to buy 5 of these Da bird replacements from Tomlinson's rather than Amazon. Also, it feels good to support a local business.
I have tried a cheaper generic alternatives to the original. My cats were completely uninterested in them. The original is just weighted correctly so that it flies in a certain way that really attracts my cats. During playtime on the day I received these replacements, I started out with the generic and then switched to the originals. The cats went from meh to full-on attack mode. That being said, out of three cats in my house, two love these things and one could not care less. I guess it depends on the cat's personality.