You get what you pay for. I wouldn't be too worried about them being waterproof however (but if you do then get GORE-TEX). One idea is to get regular GOOD boots like the Rocky S2V Special Ops Boot--AF ABU SAGE. Copy and paste that in a search engine because every time I post the link, the image is gone. They are $170, and you might need to break them in (some people said they didn't have to but I was blistered up a little for two weeks). After they are broken into, they are AMAZING comfortable. They are sturdy as Hell too. The first two days I wore them it rained really hard, so I decided to walk to work instead and wore my poncho and sloshed around in the drainage puddles. I always get strange stares but whatever. It helped break them in quicker and I didn't have to deal with the soggy feet because I was wearing Sealskinz socks which are tough as nails too. You can even check out Cabela's waterproof and snake bite proof boots that go up to your knees. I saw one for under $100, but they don't have Vibram soles, so to me, that is a severe - cool point.
Despite the rambling, if you want waterproof boots under $100, check out GORE-TEX hunting/hiking boots. If you can also find one with Vibram soles, that is the way to go my friend. Anything with Vibram is the ticket. SERIOUSLY. You WILL feel the difference, especially after 10 miles compared to regular boot soles. Why do you see the military and police force getting boots made with them?
Hoped that helped.