Well you have to compromise somewhere. Even 1970s vintage PG-7 RPG rocket penetrates >200mm steel, so if u want to survive, you have to use some sort of better-than-steel material. ERA, NERA, Composites work good against HEAT jets, but if you also want to protect against kinetic penetrator rods too, it's better to soften them up first against a Tungsten of DU plate. You could use heavy ERA like Kontakt or Relikt to do that like the Russians, but they are one time use, or you could also use complex and innovative composite armor arrays to enable all-aspect protection like the Israelis, but once hit, they can't maintain their structural integrity. The Abrams turret front has remained almost unchanged externally since the 1980s, cause the raw plate thickness and incremental updates to the internal composite arrays have been enough to defeat any present or emerging threat. In 2003 Iraq war, friendly Abrams had difficulty in destroying other disabled Abrams, even with their silver bullet DU round.
And both in the cases of Ammo or Armor, DU is indeed cheaper than Tungsten, but is still a strategic material, and the whole contamination controversy doesn't really help. So you kinda have to make your own, cause nobody will sell to you. For that you have to have a decent uranium processing industry, and above all, sufficient reserves under the ground.