You might get more responses if you repost this on the Hamfest Forum.
I haven't been to Manassas in three or four years, but the majority of these small hamfests are really just tailgate events. With the exception of folks like Joel at The RF Connection and and a couple of others, there are no manufacturer's reps or large vendors at any of them. Same deal with Frederick, Carroll County and so forth.
The only significant hamfest in the area is the Greater Baltimore Hamboree and Computer Fest at Timonium the last weekend of March. Even there, with 12-14 thousand in attendance, none of the radio manufacturers come any more, although there are several large radio store vendors, and a large contingent from MFJ.
Lon - W3LK