Unfortunately, you are mostly going to have to find sales to hit that mark if you want decent wool (flannel, worsted or the like) pants (unless of course you want something that isnt the greatest quality in the world. If that is so check out any mall brand store - banana, gap etc.). Luckily most places are having sales on wool pants now so you should hit it about right.
Hickey Freeman has some nice wool pants and I frequently find them on Sierra Trading Post for around $100 (with their deal flyer coupons). Also you can check the usual places, brooks brothers (which has frequent sales that put them right at or slightly above the $100 mark, http://www.brooksbrothers.com/Dress-Trousers/1528,default,sc.html?lid=leftnav-menu), or ralph lauren (http://www.ralphlauren.com/family/index.jsp?categoryId=1766319&view=99&cp=2943767&ab=ln_nodivision_cs7_pants)t. Also JCrew usually has wool pants (when in season) that are pretty decent for the money.
I also have heard good things about Luxire's newly started pant program. Most MTM pants are right at the $100 mark (http://luxire.com/collections/pants). I haven't tried them myself but check out this thread and see for yourself what others have said (http://www.styleforum.net/t/304965/luxire-custom-clothing-official-affiliate-thread/1140_30)