Fellas(and ladies)- familiarize yourself with this chart when considering trades during the draft:
Now, take this with a grain of salt, it's not exact, but it's a good benchmark.
I've heard people say we should trade a 3rd for the ability to get Richardson. Richardson is going to slide no later than 15, and most people think no later than Carolina's pick. No GM (outside of maybe Andy Reid in light of the Alex Smith trade) is going to trade down 10-13 spots to garner a 3rd. Even a 2nd is a bit outside the range of getting to 12.