What does "price efficient" mean to you? To me, it could mean expensive but worth it because the stuff will last, which is what you want if you are going to tour "your ass off." Thetouringstore.com has quality Tubus racks and a couple of different pannier offering, including Ortliebs. They also provide excellent customer service.

BTW...For me, and I suspect, many others, what you carry, and thus pannier size, is not directly proportional to the length of a tour. I have taken a ten day trip carrying as much as I would for a three month trip. What I carry is driven primarily by whether I will be cooking a lot and anticipated weather conditions.