Ben,
Those prices on the ND filters are very good; even with the exchange rate the way it is the grad ND filter set would cost me $60USD, which isn't bad at all for 3 filters. Assuming that shipping to the US isn't totally outrageous, then that might be the way to go.
I did a little checking around on Fleabay and I found that Quality Foto (
http://stores.ebay.com/QualityFoto_Cokin-P-Stuff_W0QQcolZ4QQdirZ1QQfsubZ2QQftidZ2QQtZkm) has good deals on Cokin-compatible stuff. Ring adapter and filter holder sets run $7.95 and individual ring adapters run $4.95. Most individual filters themselves run $10.95, with the circular polarizer running $24.95. All the prices are before shipping, which is reasonable. I've bought from them before without any problems, so I will most likely be buying at least my holder and adapter rings from them.
I did a price comparison between screw-on filters and the Cokin filters that I want and even using Cokin-branded items, it was cheaper than the screw-on filters, plus less stuff to weigh down the camera bag.
If I go with off-brand for at least some of the Cokin items, then the savings will be that much greater.
Thanks for all the help!
Heather