I bought a frame this weekend from a very nice guy who was going through something like this--he was trying to get down to 10 bikes. He had 7 custom frames built for him, so those were staying. He needed to figure out which 3 others he was going to keep. The 1983 Trek 600 I bought didn't make the cut.
Maybe you should do the same? Evaluate which bikes you ride a lot for one reason or another, which ones you couldn't possibly part with because they're so special, and start selling the rest?
__________________
1964 JRJ (Bob Jackson), 1973 Wes Mason, 1974 Raleigh Gran Sport, 1986 Schwinn High Sierra, 2000ish Colian (Colin Laing), 2011 Dick Chafe, 2013 Velo Orange Pass Hunter