Eric,
I'm not sure the market is smart enough to place such granular value on these items. Relatively speaking engine condition, panel, paint and interior, AD compliance have much greater financial impact.
Lopresti website
http://www.loprestiaviation.com/ used to have prices but not anymore.
http://www.knots2u.net/performance-modifications-10/ has similar products and can get you at least in the pricing ball park - coupled with the install time at whatever shop rate you use will get you a starting point for what the staring cost was.
IMO the speed increase values are overstated. I know my Mom flight tested all the mods on our aircraft and only kept the ones that did increase speed as we were prepping for a world race at the time. Don't have her data for the flight tests. The rudder gap seal was the last one and it actually slowed our 39 down so it was removed. If it were not for the races, we'd have made different decisions.
My personal favorite has always been the WOW cowl as it dramatically improved engine cooling. The bottom panel also aids access to starter without removing the entire cowl. Really, really, really tight flexible baffles also have as much as a 50 degree cooling benefit but do take hours to install.
A good tailwind will trump any of the speed mods. Flying were the winds are best is free.
Being able to fly non-stop is also better than any speed mod so look for tip tanks as a performance mod.
As a happy 39 owner and having raced a 30, a 39 is a 'newer' Twin Co but when the years are pushing 40s and 50s, not sure a 5 or 10 year difference counts for much unless you want the later cabin configurations. The 39 does buy you the no critical engine benefit.
Hope this helps.