I've never used an RV consignment lot but I have used consignment dealers for other large ticket items.

Here's why I would use a consignment dealer:
> I don't want to be bothered with selling the RV
> The RV is taking up needed space at my property or I'm paying to store it but no longer use it.
> Eventhough the consignment fee may be as much as 25% of the final selling price, I don't need that money. In other words, I can afford to pay someone else to sell the RV.

I would sit down with the consignment dealer and find out:

1. How they plan to market the RV.
2. How long does it normally take for them to sell an RV.
3. Set a beginning price, a negotiate to price and an definite no less than this price for the RV.

If it hasn't sold in several months I would relook at the price and adjust down as needed.

A consignment dealer is a great way to get the RV out of your space and onto their lot plus you don't have to deal with prospective buyers.

The biggest issues are how high is the consignment fee and how well do they try to sell the RV.  If you are paying 25% of the sales price, I would expect an aggressive marketing effort by the dealer.  If the fee is only 3%, I wouldn't expect much of an effort.