Where can i buy LOTS of shotgun ammo?

Well i want lots of 12 gauge ammo i like to shoot A LOT.I was thinking maybe a website where i could buy 250 buckshot and 250 slugs for under $150 each if possible.I can go to walmart and buy 100bird shott for $20 but you knowbird shotssaren'tt fun if you shoot a bottle you get a few holes buck shot you shoot a bottle you have a piece of plastic left.So what are some sites?i found midwayusa has 250 buckshot for around $180 but that's a little overpriced