Ok, so I thought, maybe the HST price difference was a fluke. So, I looked up 147 gr Speer Gold Dot, which both also happened to have in stock.
Price difference was similar with the price advantage again going to sgammo.
$775 at ammoman incl shipping - 9mm Ammo - 1000 Rounds of 147 Grain JHP Speer Gold Dot 53619 with Free Shipping at AmmoMan.com
$537 at sgammo incl shipping - 1000 round case - 9mm Speer Gold Dot 147 grain Hollow Point GDHP Ammo 53619 | SGAmmo.com
I've not used Ammoman either, but I'm on Target Sports mailing list and they offer free shipping on bulk orders. SGAmmo still beats them on price with shipping, although not by as much as what you're showing for Ammoman. I think I'll stick with SGAmmo.