The glass nail file I was given several years ago having snapped in half, I tried various sources for a good replacement (eBay, the local chemists...). The files I got from there, though cheaper, were inferior in quality and quickly lost their filing powers, which in addition to them being better for your nails is the reason I was looking for a glass one in particular in the first place.
This file, however, does not disappoint. It should last for several years, so is worth the initial investment.