That's funny because I'm actually about to jump back on the 300blk wagon. In my area it has been getting easier to find ammo, even Walmart had the Remington boxes for $18 (that's less than $1/rd!!). The last gun show also had plenty of 300blk ammo for sale, but a little bit more not surprisingly.
If you want to get on the 300blk boat, get ready to pay a premium for ammo or start reloading. I know you can buy ammo online now for $30/20rds all day, just look around.