I found a good pair of gore-tex rain pants at my local Filene's Basement store. I jumped on the deal at $20! Followed that up with a pair of stretch-fleece knickers from Eastern Mountain Sports, and the system works great. Caught the fleece on sale also, so in my world this is a major bargain. I am an old-school guy who learned in 1966, skied through the 1970's in blue jeans, and I am loath to spend huge money on gear. Yes, my rear end has frozen to the chairlift, more times than I care to remember. But I am older and wiser now.
Anyway, don't give up. Think of places to buy non-ski stuff that may transfer over. My gore-tex works well, holds up against the ski edges, and has lots of room to move. They might have been golf or boat pants. I also have a pair of hunter's pants that are for the worst of days. Also gore-tex, black but with a camo reverse-side. Hideous, yes, but on the really bad days, form follows function. One last tip: Campmor (in NJ) has a lot of good deals on Columbia and other makes, and are online and in a catalog. Good luck, and happy bargain hunting.