From looking at posts on govplanet.
2011 MEP-802A SET - $12,797.70
2011 MEP-802A PU - $16,256.00
2011 MEP-802A PP - $46,322.00
2013 MEP-803A SET - $10,700.00
2013 MEP-803A PU - $17,730.00
2010 MEP-803A PP - $77,690,00
2006 MEP-804A SET- $16,160.00
2004 MEP-804A PU- $18,183.00
2006 MEP-804A PP- $74,134.00
2010 MEP-804B SET - $26,334.00
2009 MEP-804B PU - $20,415.00
2009 MEP-804B PP - $53,500.00
1998 MEP-805A SET - $26,705.00
1999 MEP-805A PU- $28,521.00
2012 MEP-805A PP- $63,941.00
2010 MEP-806B SET - $25,073.00
2008 MEP-806B PU - $44,185.00
2006 MEP-806B PP - $96,819.00
2007 MEP-807A - $67,000.00 (Couldn't find enough examples to tell if this was a SET or a PU that had been taken off a trailer)
Some clarification(Keep in mind this is just what I gleaned from browsing the govplanet site).
SET means just the generator by itself with no trailer.
PU means "Power Unit" or a generator with a trailer.
PP means "Power Plant" this seems to have 2 designations.
1. For the 802 and 803 this means 2 sets mounted on 1 trailer with an AC synchronizer.
2. For 804 and up this means 2 sets on a 2 trailers with an AC synchronizer, however several were being sold as a pair so possibly they were sold to the military as a pair.
A note from me, I can't figure out for the life of me why the 804B by itself is more than an 804B with a trailer but I confirmed it with several postings so I don't know.
Another note is it doesn't seem to matter what year the unit was made, I found Libbys from 1993 cost the same as a Fermont from 2013. That also indicates it doesn't matter exactly which manufacturer produced the unit.