What "WaveBB" was trying to explain is that a $25 UV filter is negating the affects of his $1k+ lens. GOOD filters cost upwards of $100 (and yes, in the world of high-quality optics/glass, it really does make a difference) and to outfit all of his lenses, would easily cost $500+. Take a look at some of the good filters on B&H - they ain't cheap.
That being said, for the 99% of us who use mid-quality gear, a basic UV filter is a wise investment. Most importantly, it will protect your lens from scratches, dust and moisture. But, as mentioned, if you're using high quality glass, get insurance or get a better filter.