I looked forever for "cheap" .357mag.
I was about to order 500rnds of S&B FMJ 158gr when I happened to stop by a local gun store and found Fiocchi 142gr. for 17.95 a box of 50. I bought as much as they had. (about 1,000 rounds) Keeping the casings for reloading of course.
Just goes to show you, keep looking b/c you never know where you will find it cheapest. When you do, and you will know, buy it. It was very hard for me to be patient.