I've been through this before and the worst thing possible is to try guessing what folks want. You could prepare a bunch of work with gloss finish and satin is what folks are buying. You could make 12" and they all want 6". Prepare as many nice pieces as you can, showing options and displaying photos. Bring a bunch of business cards, get some other something to pass out. Hold a drawing for a beautiful bowl or set or ?? and use the sign ups for entries to start a mailing list -- GET THEIR EMAIL on the entry form. Try to sell commissioned work. The work you get will be sold and the there will not be inventory that did not sell.
IF the money is bothering you -- and it shouldn't -- $140 is CHEAP exposure for the potential of 15,000 views of your product and advertising. You could not buy that good of an ad in the newspaper or the TV for that price.
Good Luck and let us know how it goes.