I have never added boning to a sewing project, but soon I will be. The boning for my dress came the other day. I ordered it on eBay for just under $5 for 5 yards (including shipping) I read that it is better than the boning I can get locally, it does feel sturdier and flatter at the same time. I beleive it is called rigiline boning.
I probably won’t make the dress until summer or fall but I am getting stuff when I can find it on sale or use a coupon.