I don't need a lot of steel core, but it's handy to have if you need to poke a hole in something a little harder than an animal. When Federal Green Tip prices went high......
I bought a bunch of ZQI branded 5.56/62gr steel core (NATO SS109)at Walmart. The cost was $9.95 per box of 30, so about $0.33/rd. It's made in Turkey by a company called MKE - a reputable company over there. Loading a mag with both the real Federal Green Tip & ZQI, I couldn't detect any shooting difference at all. Same POI at 100 yards. Certainly not an amzing price, but just low enough for target practice, without having to resort to steel cased ammo.
Twenty boxes (600 rounds) fit neatly into one those cheapo plastic Plano boxes also at Walmart.
FWIW, I also buy and shooot ZQI ammo in 9mm and 7.62x51. Been happy with all of it.