my mistake -- it was not £18 ot was £16.50!!! www.purelyhealthdirect.co.uk - item 5058, Glucosamine Sulphate 1500mg Ultra Platinum Strength (single tablet).
As for 'cheaper' products, it is not that... as long as you've no great intolerances allergy-wise these generics are better. Think about it: i just bought 16 ibuprofen 200mg tabs for 39p (and that was at Waitrose: Tesco has them for 24p!) and in comparison the Nurofen are almost £2!!! Why? Packaging, advertising, shelf-space, and, more often than not, additives.
Most glucosamine out there is packaged with MSM or Chondroitin or multi-vitamins which, for ME, are not required or desired: i eat very well, usually, loads of fruit and veg, plenty of fish, etc so don't feel a need for most of those things
as for 3000mg a day of Glucosamine, well, I doubt it... my osteo says 1500mg a day and i am at the moment in injury recovery mode (please, all at once: Poor Daniel - hasn't run in 10 days and is slowly preparing to explode!)
I don't think the body can deal with / process that much (sort of like vitamin C: much more than 500mg daily comes out in your urine) so more than 1500mg is likely a waste (and may be bad for you, but I don't know that for certain).