I'm currently paying just under a grand per 15pt unit (Postgrad level) and there's no way the study materials are worth that, although they are quite good and up to date.
The study materials are more costly than you might think because they're done in such small numbers. More pertinently you're not paying for the study materials, you paying to do a credible assessed course. Getting people to mark stuff and ensuring standards is expensive. The OU is actually remarkably cheap compared to most alternatives.
Personally I think it represents excellent value for money.
I failed my first exam of the second module by 1% which is absolutely gutting. I got a grade B equivalent for the coursework which makes it even worse! It turns out a lot of others failed the exam too, so at least I am not the only one, but that doesn't help. Failure rate for 2009 was up by 14% apparently which is considerable. There could be a number of reasons why. But I am to re-sit in April, and then I have another exam for my current module, which is due on my birthday, 16th June. If i pass, and at the moment that's a huge if, I will be half way through. It has gone very quickly, but I am putting about 30 hours per week into my studies at the mo, which is a lot. I hope it pays off, otherwise I must be fick.