$100 is minimal for a mic of any quality. Shure SM45 is a common musical stage performance microphone that we use at school and it retails around $100 if I recall. They're durable as hell and sound decent. We use Audix mics for high quality recording, which run us about $300 each.
I don't even know if $30 is going to get you an XLR... I know common PC microphones (stereo minijack) range from $10 for mono to $20 for stereo and sound like butt.
For boom use and camera use, we use stuff in the $60 range. Check out BHphotovideo.com and see if they have anything that looks appealing.