I just ran a batch of milled parts using some 12L14 square bar which I had on hand from long ago. When I went to buy more, I was surprised to find it 1/2 again more expensive than similarly shaped AL 6061, at least in small lots on the web. As I started looking at steel prices and availability, I found few highly machinable alloys in square/rectangle bar (1018 is common but not a lot else; some 11L17 or 1117) and prices generally higher than aluminum. There is more variety and availability in round rod and I've bought 12L14 for turning with no problem. Am I just looking in the wrong places? Is there no market for steel for milling prismatic shapes other than 1018?