I usually do better buying practice ammo at WallyWorld, but for SD ammo I've had a lot of luck/better prices at Ammunition To Go. Inventory varies from day to day, so you have to check back often (for 9mm etc). The less used calibers (45, 357 SIG etc) they often seem to have on hand.
If you can get a few buds together to share shipping costs, prices ain't that bad (prices being a relative thing these days).
FWIW, I often toss X number of boxes in the cart to see how it affects shipping-here's what I found last time (all 50-rd 9mm boxes):
TOTAL SHIPPING SHIPPING PER BOX
1 box $8.65 PPB $8.65
2 boxes $9.33 PPB $4.67
3 boxes $9.68 PPB $3.23
4 boxes $10.12 PPB $2.53
5 boxes $12.75 PPB $2.55
6 boxes $14.11 PPB $2.36
7 boxes $15.04 PPB $2.15
8 boxes $16.16 PPB $2.02
9 boxes $17.24 PPB $1.92
10 boxes $18.34 PPB $1.84
'Course, this might change slightly depending on the weight of the calibers you're shipping (although I don't think it makes a lot of difference)?
You might also check local police supply stores in your area? I can often get good prices from a couple of police supply stores in my area.