I've bought a wig from that seller before, and they are BEAUTIFUL wigs. the quality and style is fantastic - just be warned if you're going to get a "silver white" one, it's NOT white at all, it's a solid silver and looks very very dark when compare to true white extensions. I got that one, but with bangs (same length) and the longest part comes to just above my tail bone, and I'm 5'10". they're great, I highly reccomend them.
but yeah, you're really not going to find a wig that long for under $50, unless it's really poor quality.