BRB member Richardmcarr has done some bang-up work putting together a spreadsheet which utilizes Pro-Football-Reference's Approximate Value stat. As with any football related stat that isn't a counting statistic, it's not perfect, but using any objective reference point is going to be helpful when it comes to football analysis.
While Richard (if that's his real name [snickers]) posted his hard-fought (seriously, this work took a lot of blood, sweat, and tears, I'm sure) research in a FanPost, that's probably not the best way to share this data. I dropped him a line yesterday, and Richard was kind enough to agree to share his findings.
Thus, here's a Dropbox link to Richard's work. Feel free to download it and work with the data. Use this thread (or his) to share any insight you might gain. If you'd like for me to share more documents, please feel free to send me an email with the file attached.
Knock yourselves out, BRB, and thanks a ton to Richard for his fine work.