I can't even remember the last time Ebay sold brass. I know it has been a while though.

Here is about the best price on processed once fired brass:
http://www.scharch.com/products.php?cat=9

I have friends who shoot a bunch of 223. They collect their brass and bring it to me. If that fails I pay $5 to hit the local range and pick up brass there after I ask the shooters if they are keeping it. Most times they are not so I get plenty on the days I hit the range.

As far as when to toss the brass, most have hit what I look for also. Loose primer pocket and they go as well any neck problems. I have recently started annealing my brass so hopefully that will cure some of my neck issues. None of my loads were close to max also and the first problems I was seeing are neck issues. I haven't had a chance to fire a few hundred of the annealed brass to see the annealing helped but I am sure it did.

Dolomite