That price for Tru is never going to happen.
I doubt the Rams can extract DeCastro for Tru straight up. It wouldn't be a value issue but rather the cap costs to the Steelers and I have no idea if they have a good replacement on their roster.
But if the Tru to the Steelers thing is even in the cards (I seriously doubt it) we'll get a better idea of the Rams' motive for doing it according to what they get in return. If they get like a 3rd or maybe 2nd round pick, then this was to clear salary cap to sign other players.
If they were to get DeCastro for example, then it tells me that the Rams are trying to make immediate improvements to the team.