What I found most interesting though was the chart below that showed how mission costs could be plotted as a combination of weight (as a surrogate for design difficulty and cost of procurement, assembly, and test) and mission difficulty. Large missions in the Cassini weight class would range from ~$3B-~$7B depending on mission difficulty. What is immediately obvious is that missions that begin to exploit the launch capabilities of the Constellation system would likely fall in the $5B-$15B range. Such missions would eat up the entire science budget of NASA for years. To a lesser extent, missions using the Delta IV heavy launcher would also dominate the science budget. My reading of this is that the science program is budget constrained, not launch constrained.
From page 6 of the report. Click on the figure for a more readable version.