Expect to pay about $50-60 plus core for them. They are very cheap, and pretty easy to install yourself. The only problems the first time around is that you need to buy a pittman arm puller and a 32mm socket, and sometimes some of the bolts are frozen and a complete PITA to get out.

Once you've done it the first time, it is easy and very cheap the subsiquent times. Now is the perfect time to learn how to do it yourself if you ever want to.