Yeah, compared to other saddles, b17 are priced fair. The main idea behind brooks saddles especially the b17 for wider sit bones, is that you break it in and it is "molded" in your shape, basically custom fit for you. Plastic you can't really break in. If you find plastic comfortable, go for it, but if you're looking for comfort, I really suggest Brooks, especially since you have wider sit bones, since the b17 is wider compared to most other saddles. Well, maybe not the ones for breach cruisers.

If you're really that tight on a budget, seriously, go to the LBS and ask to try out their saddles.