Someone on Steam (sorry I don't know which nickname you have here on SE Forums) talked with Steam Suport and got this answer:

I just talked with an agent from their chat support, he said it indeed looks like an error after i showed him the others games prices and the psn blog post. He said he couldn't do anything right now but he would escalate it to be investigated better.

Also posting in the official forums should help a bit, since the community managers and game masters often read and reply people posts there.
So it's means that is SE's mistake on price, 'cause if was Steam's mistake they could fix the price right after this conversation