Umm I wouldn't normally do this but since this forum seems to be discussing PLA offers in depth and since we have big volumes to fill.... I just noticed smoke coming out of the back of my bench power supply, flipped it around and saw that the ventilator wasn't turning. This hot weather is a good test of that sort of thing. Of course there are now all kinds of doubts as to exactly what has melted and, putting down the screwdriver, decided to check the site where I bought it to see what sort of guarantee there might be. Fell upon the following: http://www.circuitspecialists.eu/sale-promos/?mgproducttype=90 Make of it as you will.
Long term our machine is going to be for student use, a cheap source of reliable print material for prototyping is going to be key for me. as well as good quality materials for final product prints as well especially for our A Level product design groups.
If you are going to be a long term quantity consumer and perhaps are able to talk openly about your suppliers, I'd approach some like E3D and Printme3D directly and see if they will do education/quantity discounts in exchange for some free promotion around your student base. When I had a business we used to do lots of discounted work with schools in exchange for flyer drops, mention in internal publications etc, plenty of students and students have parents etc etc it was effective advertising.
E3D were very helpful when purchasing the BB, and did give an educational discount. and it applies across the board i think for parts and consumables. I remeber being warned off cheap filament on things like eBay as the quality control was poor, and the filament thickness was not consistent and neither was the quality.