The way I see it, if I sell my own brass and buy pre-prepped brass, all I've done is sub-contracting the prepping, to someone who might very well be better equipped and therefore do a better job than I would, all for a few pennies. Essentially, if I had enough brass, I could send it to black sheep (or anyone else with a camdex), he does the prepping and charges a given amount, say 10¢ a piece, and sends them back to me. Or I could sell my non-prepped brass on the EE, then outright buy from black sheep, and the cost to me is the difference in price, so, say 10¢. Doesn't matter which route I choose, I end up sending non-prepped brass away and receving prepped brass, all for 10¢ a piece.
Then the first 7000 pieces are free compared to buying a giraud. And all the time you've saved can be spent shooting instead of prepping.