The importance of good materials
I'm sure many talented people give up art because of the ugly results they obtain with substandard materials. It's worthwhile to remember that 90% of the art supply market is geared towards hobby artists, who the manufacturers clearly regard as undiscriminating, so don't expect to get good paper, paints or anything else for amazingly low prices.
Of course, on the other hand some materials are grossly overpriced, designed to take advantage of the quality-fetishists amongst us (like me) by making all sorts of extravagant claims--and you don't get your money's worth with them either. More expensive isn't necessarily better. Sometimes the most exotic and exorbitant product, particularly when it claims to be 'the secret ingredient of the old masters', turns out to be decidedly unarchival. I recall a sobering experience a while back when I excitedly spent a considerable sum on iron gall ink from an obscure supplier in England. It came in lovely little glass bottles with corks sealed with wax, just like the 'olden days'. Sadly it proved worse than useless as a little research revealed that this material is ultimately corrosive to paper.
It makes sense to be sceptical at the low, middle and high end of the market. The best idea is to research what constitutes decent-quality materials and be highly suspicious about manufacturers' claims--don't believe what you read unless it's substantiated and do your own research so that you can't be 'blinded with science'.