No way Flacco has earned a Rivers/Eli/BenR type of contract. That said, you won't get him to agree to a deal anywhere near a Kolb or Cassel deal, even if they were egregiously overpaid. Plus QB is the one position where a failure to get an average or slightly above-average player at minimum, guarantees failure (barring a time-machine and an all-time great defense). So you hope to sign him in between these two levels, but would be forced to sign him at the higher level if push came to shove.

From that point, if Flacco keeps improving, you signed a fair to eventually-cheap deal; if Flacco fails to develop and plateaus at around where he is, you overpaid at the position fairly significantly.

If Flacco insists on a deal that is bigger than Rivers/Eli/Ben then I think you make him wait until 2013 and take your chances.