“No, dummy, price-fixing is a crime against the buyer, which is X, so they do have standing.”
I might be a dummy, but even I can understand that in the case at hand X is the SELLER of advertising, not a buyer. You seem confused.
“SELLER of advertising, not a buyer. “
You still do not get the advertising industry model at all.
X sells advertising but gets it from advertising management companies who refuse to transact with them.
You should take a class in economics and civics.