Howard - I don't see anything wrong with your ad. Your unit appears as good as or even better shape than the one my son had in the pics. I don't know if that really pushes the value up any more. And like so many things, when several start showing up the value and what someone is willing to pay often slips down.
What I will say and I'm sure you know, is that sickle bar mowers are generally used for a somewhat unique mowing situation. Something that is difficult to mow with a more standard mower. I'm gonna bet that half the people looking for one have that unique situation where they think a sickle bar will solve their problem. The other half of the people looking for one are probably collectors and are matching it up to a classic tractor for shows. Your unit looks like it could fit into either situation.
As for working out a consignment, I really don't see how that would help/work. I'm located in the Phoenix area and my son is in Woodbury, CT. I see you're in Clarks Summit PA (close to Scranton) so only a couple hundred miles from my son. I'll let him know about your unit in case he comes across someone looking.
My only other suggestions are that you'll probably have to adjust your price. I'd separate the belly-mount mower since I really don't think someone would want both units. Also, from the comments I've seen you probably need to provide some kind of shipping support, at least be willing to strap it to a pallet, maybe take it to a Fastenal store (although I don't know how they do their shipping or costs but they apparently have some cheap freight price for store to store). There seems to be interest in IL, WI, maybe even OH.
And the other thing, since the Forum rules don't want you posting something you put on eBay, I'd suggest you put a time limit in your ad, that if it doesn't sell by a certain date you're gonna post it elsewhere.
Good luck selling your unit.