1st rounders are the only ones who make 7 figures, I believe. I know these super sophomores are making somewhere in the $1-2 mil range, but guys only in the 3rd are making about $700,000. Vick was a 5th and he makes around $500,000. League minimum (undrafted rookies who make the 53 man roster) is $380,000.
I'm not going to sit here and say there isn't a big difference in pay between each round because for a guy like me that's a big difference, but relative to what these guys are going to make it doesn't matter. If he's a late 1st rounder or a 2nd to 3rd rounder he'll make around the same. It's not about the money. It's about getting recognition for your hard work, and truthfully I'd rather go in the 20-40 range. Better chance of going to a team with a good QB and a shot at winning immediately.