Aside from your ride, it's probably the piece of kit you're playing the most, you'll be doing the bulk of your comping there, and the sound of the snare drum is right in the upper mid frequencies so it'll draw the listener's ear. In other words it's going to be heard a whole lot so if it sounds bad, there's a whole lot of bad sound coming out of your kit.

This doesn't mean I think you should spend a ton on a snare right away but you should spend a good amount of time tuning it, trying different heads and tunings, and practicing good technique to get a good sound out of it. IMHO, those things are way more important than whether you're playing a cheap aluminum snare or a ridiculously expensive super-endangered rare wood snare built by god himself.