I think people do look at comparisons. I could be totally wrong, but I'm thinking maybe the people at craft fairs, or people that buy homemade soap in the first place, are the type of people who care about what they are using on their bodies, people who look at ingredients and check labels, etc. Again, I could be totally wrong, but I know that for me a love of all things homemade, and taking notice of the makeup of products I use come hand in hand. If I noticed someone's soap was cheaper/pricier than someone else's, I would want to know why. I would wonder if the more expensive soap was better quality, or if the less expensive was lower quality. Besides, I wouldn't just buy a soap based on price; I would look at color, fragrance, oils, weight, ingredients, etc. Also, people won't always just buy a cheaper bar of soap simply because it is cheaper. In fact, when faced with the option of a cheaper vs. a pricier soap, people will sometimes intentionally buy the pricier BECAUSE it is pricier, and thus (they assume) a better quality. Of course, that's not always the case. It's all marketing, but that's a whole 'nother deal... Anyway, if your soap is priced fairly and according to its value and customers agree on its worth, I would stick with the price you put on it. You might want to go and check the competition's wares as well, to see why they are pricing the soap how they are pricing it.
Still, I'm not in your place and situation, (and I never have been in it) so I can't tell you what to do.
But since you're asking for opinion, I would say next time you're in such a situation, keep your soap at the initial price you put on it and watch customer traffic between your soap stall vs. the cheaper one. Customers are the ones, after all, who have the final say on what customers are going to like.