I think I understand what Awaclus is saying. Messed Up Highway introduces an effect on-play, and the effect is only active while the card is in play. But it doesn't state when the effect ends, so that effect should come back the next time you play that copy of Messed Up Highway (along with a new cost reduction for a total of a $2 reduction). I think that's a perfectly valid (perhaps even the best) interpretation of the text.
However, it has obvious tracking issues. There's no good way to track how many times you've played a Messed Up Highway, nor is there a good way to track which copy is which. And cards that have severe tracking issues as part of their everyday functionality don't get published.
To fix the issues, you would of course specify when the effect ends. "Until this leaves play, cards cost $1 less." And then make sure it's a non-Duration card so that it gets discarded during Clean-up. Of course the friendlier, nearly-identical phrasing is, "This turn, cards cost $1 less," and that's what Bridge has.