Well.....
You can get powder for anywhere between $20 - $50 per pound.
You can get bullets from $150/1000 - $300/1000
Primers can be had for $30 - $45 per 1000
Brass can be free to $70/100
So.......it doesn't cost much, unless it does.
Oh, and you'll need a press, so count on another $150 or $1000.