I expect HiTech filters are cheaper from the UK - that's where they are made.
Formatt Filters website is
www.formatt.co.uk but the site appears to be down just at the moment.
Their filters are the same price at
http://www.teamworkphoto.com
They are quite good. I have a 3-
stop hard grad, 3-
stop reverse hard grad, 4-
stop ND and 8-
stop ND.
Do note that they are not colour cast free - when you stack or have the equivalent of around 6-
stops you sometimes get magenta colour casts. Not a huge problem with solid ND filters as the whole image is affected evenly, but with the GND's it can be fun to remove. I find them adequate for my needs and certainly cannot justify the cost of Lee or Singh-Ray filters (and Lee don't make 85mm filters which I use anyway).
I find Cokin perfectly fine but unfortunately they don't do hard grads (nor NDs more than 3-
stop).