Ball joints:how much should i be paying?

I have bought from Rock Auto twice. Pleased both times. One thing I noticed (at least for shipping to US) is that they do not combine shipping costs with items on the same order from different warehouses. Thankfully, they have a really good "shopping cart" that shows you which warehouse each item is coming from, and the shipping cost broken down by item. Sometimes I have purchased a more expensive part, and had it be cheaper overall because it came from a warehouse where my other parts of the same order were being shipped from. So if your order shows parts coming from two or more warehouses, try selecting different brands to see if you can get them all from the same location, and save quite a bit.