Petco has it on sale through today on their online store:http://www.petco.com/product/10533/C...-for-Cats.aspx
Price is slightly higher than Pet Solutions, but no shipping charges so it will be quite a bit less. I'm just starting using this to try to get my newer cats and older cat to get along better. Older cat is also quite shy so hopefully this will help. I think I'll order one more diffuser and the pack of refills while it's on sale!
Edit - I just noticed that the free shipping only applies to the kit, not to the refills. But the 3-pack of refills is a good price so even with shipping (which is substantially less than the Pet Solutions charges by the way), it's a pretty good deal.