shawarms.com is not charging sales tax to out of state buyers presently. They have Winchester, PMC, and MagTech 9mm at $13.99 per 50-round box. Shipping for a 1000 round case is $14.95, which brings your delivered total to $294.75, or $14.74 a box.
sgammo.com has the same ammo for $20 less per 1000, with free shipping, but you will have to add sales tax into the final delivered price.
targetsportsusa.com has PMC, MagTech, Blazer Brass, Aguila, Sellier & Bellot, all at the $260 price point per 1000 with free shipping, but plus tax. Remington is at $270 per thousand.
These prices are about as good as you'll get for name brand ammo from a reliable seller. If you find something lower, let us know.