I'll start by disclosing that I have NOT reloaded steel.
That said, I just ran the numbers on the shells I reload for casual skeet shooting (12ga, 1oz lead). A case of cheap factory loads (250 rnds) goes for $55-$60 around here. Assuming free hulls (The key here is to buy shells which are quality enough to reload), I can load 250 rnds for $40 in materials. The savings over factory loads pays me about $4/hour to do it, but I enjoy it. I use a Lee Load-All II, so my equipment cost has long since been recovered. I need to get something better one of these days....
I suspect the savings would be greater for steel, as factory loads are so much more expensive. Of course steel shot is also quite expensive. However, if there is really no decent 3" hulls around as the above poster mentioned, buying new hulls would likely eat up most savings.