how much does it cost to fix or replace the side view mirrors?

[AllistarEvans]

my left side mirror has a huge crack that starts in the middle and goes in four directions but the power still works, it just looks like it needs a new piece of glass. today i just hit another cars side mirror with my right side mirror on a two way road with cars parked on both sides. i just checked to make sure the power works. it makes noises and sounds like it functions properly, but there is no glass there because it was yanked off and there's no way to know until its there. so lets assume that i just need two pieces of glass for both side mirrors. how much is this gonna cost?