My advice? Listen to your gut instinct. We have it for good reason:) Whenever I've ignored mine because of the possibilities I thought there might be, or how good things looked on the surface (turned out they weren't so good) I have always gotten in the soup. Every time.
There's a business principle that a fair deal should be fair for both parties. If you really don't think it's fair for you, I'd take a pass. Possibilities are nice sounding but they don't always pan out. IMO, you need more than a maybe future possibility that hasn't yet been discussed. I don't make business deals based on future maybes. Also, people who try to take advantage upfront usually don't change down the road.
That said, how much negotiation have you tried? Have you tried negotiating a better price? Have you offered them their desired consignment price if they purchase your soap for use at their Inn?
They're in business to make money, not for charitable reasons, and unless you're a charity, neither should you be.
Edited for clarity, typos and to add more.