It will pay off for you to do your research here. There are at least 3 different 50mm lenses available from Canon (f/1.8, f/1.4, f/1.2). Though you might just be looking for a specific focal length, these lenses vary greatly in their quality, chromatic aberration, vignetting, and bokeh. Maybe none of this matters to you, but the price differences will range from $100-$1500.
Check this site out for extensive reviews on each lens.