The Bears realized it's better to take a risky shot at a top end QB then hang out in no mans land for years and years with Mitch and Nick Foles and Andy Dalton.
I think the general consensus is that a future 1st round pick is like a 2nd round pick in the current year.
If the Bears had made the playoffs last year, then the trade looks completely fair by the values.
If Justin Fields is a great, franchise QB, then the Bears fleeced the Giants.