Just picked up a Brooks for my Brommie at a bike swap the other week. $15. It's slightly 'distressed',but serviceable and still had alot of life left in it.

Just gotta look around. Heck,a friend of mine once picked up a completely haggard bike for $25 at a yard sale because it had a decent Brooks on it. Pulled the saddle off and gave the rest to some friends to make a freak bike.