Try tack trader pages on facebook. If you look carefully, you can find lots of good deals there. Some folks that outgrow things, get out of riding, or are even selling brand new breeches for a low price because they ordered the wrong size. I sold a brand new pair on there for $20 shipped because apparently x small is not a popular size. Beats getting nothing for them sitting in my closet! I also bought a pair for the same price in basically show condition. Also consider posting an ad in the classifieds on here. Same deal- lots of people end up with extra pairs of breeches and some money is better than nothing. You'll sometimes find some of show quality, and even more schooling quality for really good prices.
And, of course, check the sales pages of online stores. I'm sure there are going to be lots of sales on winter breeches soon, and regular ones go on sale regularly as well.