Well it depends a lot from the fact where you purchase your filament. Larger quantities of cheap filament won't necessarily produce more parts than lower quantity of pricy filament. I had a lot of terrible experience with cheap supplies, they can have as low as 50% efficiency in producing good prints, on the other hand when printing with high quality filament you will get 95% efficiency or even more. Not to mention cheaper filament can steal you a lot of time with fixing extruder / hot end.

I use 2 suppliers, one is from UK and they produce the best filament in my opinion but they are also pretty expensive so I only use it for highest grade prints. Another is from the Netherlands, their quality is pretty fair and they are cheap (around 20€/kg + shipping).

- Filip