How GMs value certain positions

I've been wondering ever since the Seahawks drafted Aaron Curry, as I'm sure many other FG readers have, just how valuable certain positions are compared to other ones.  Are LBs easily replaceable, and are they like halfbacks of the defense, dependant upon the line in front of them to a great, but varying degree?  I'm not sure how to accurately measure an individual position's value (not sure anyone one will ever be considering football is so team-oriented), so I instead decided to look at how GMs value different positions by three things: draft value, monetary value, and cap value.  GMs can say one thing about how valuable a certain position is, but when it comes down to it, actions speak louder than words.  Put your money where mouth is. <insert another overused cliche> etc.

First thing's first.  I looked at the 2008 rosters and the cap number and the salary amount associated with each player for the year.  In some cases, I looked at the numbers for every player, and in some, I looked at the numbers just for the top at each position kind of like franchise players except instead of the top 5 players, I looked at the top 10, or what I thought was the top 10 equivalent.  So I looked at 10 QBs, but only 5 FBs (because they only play on 50% of snaps roughly), 25 WRs ( to account for 3 and 4 WR sets) 10 TEs (for 2 TE sets as well as 3 and 4 WR sets), 17 DT (because of 3-4 defenses), 23 CBs (for nickel and dime packages) etc.

Sometimes the positions are broken up as LB and soemtimes they are OLB and MLB or OL instead of C, OG, and OT, don't ask me why.  It just has to do with the data I had, and the amount of searching I was willing to do, since It's really hard to find info on whether or not a backup RT that never played more than a few snaps is a RT, or a LG, or just a utility OL with no specific position.

Here is the chart and data of how much money an average team spends on a player on the field at each position as a percentage of the total salary or cap value of the team.  So even though there is only 1 QB on the field, I have all 3 QBs on the roster as the dollars spent on the 1 spot.  and even though there are 5 CBs on a team, I have 5 / 2.3 (average number of CBs on the field on any given defensive down).  Note that this pretty much disregards special teams.  This data has every player from 2008.

One player as a percentage of dollars team spends

Percentage Data summarized.

Here I looked at just the top players, rough the top 30% of starters.

Top 30% by Salary

Top 30% by Cap Value

Next I looked at draft value, since this applies more directly to the Aaron Curry question.  I used the Draft Countdown trade value chart

for the draft value numbers, and looked at all the drafts from 1970 to 2008.

Average draft value of the first two rounds

Average draft value of the first five rounds

Data in Summary form

Again, I didn't do any interpretation.  I just thought it would be a fun project to do.