Yeah. I own Robocop and certainly didn't remember that line in it. Guess I just assumed it was a common phrase that's always been around.

You are forgetting that Robocop is in the future, thus they would have already seen this McDonalds's commercial in '07.

So yes, Robocop ripped off McDonalds. We just didn't know it yet.

There's no actual proof of any connection, and for all I know nobody associated with Robocop ever read or even heard of "The Marching Morons." From what I remember about the "Morons" story, over the centuries society has continually degraded until, as the title suggests, pretty much everyone is a moron.

In "Morons," the public buys shoddily built cars that look sleek and sound fast, because all they care about is how they look. In Robocop people drive the all new 3000SUX.

In "Morons," popular entertainment has devolved to the point where the most popular TV show consists of pretty much nothing but a guy saying, "I'd buy that for a quarter!" The TV show shown over and over in Robocop seems to consist soley of a Benny Hill type character surrounded by scantily clad women, who leers at them and constantly says, "I'd buy that for a dollar!"

I grant you all that the phrase probably existed well before either the book or movie, but the similarity of the TV shows in both always seemed deliberate to me. I've always felt it was Robocop's homage to Marching Morons. But who knows--it could just be a coincidence.

I have to disagree here due to the value of the dollar. It is taken to be sarcastic and if the value of the dollar is high, which would be the case pre-'51, it loses its connotation.

Exactly. See the term: Popularized
Another great example is "yada, yada, yada" which definitely pre-dates Seinfeld, but Seinfeld made it their own and popularized the phrase.