I do 8-10 shows a year all over Canada and take new stock almost every time which means that I have to price everything beforehand and never have a problem doing that.
If I price too low then thats the way it goes, as I apparently did not do my homework. It happens.If it is too high then people can make an offer or I will change my price tag during the show.
After every sale I remove my price tags as I know that certain markets bring higher or lower prices and things will be different next time for many things.
I have a ton of stock as I am constantly doing estate work so things change on my table constantly.
I think that it is courteous thing to do for your customers and the extra work is well worth making then happy.
It also helps if you have to leave your table for either a bathroom break or just a break, and ask either a partner or fellow dealer to mind your table for a few minutes. Nothing is more infuriating to a customer than to go to a table where the dealer has stepped out and find out that his replacement has no idea about prices. As a customer...I hate that. As a seller..I will lose money.
There is a woman in my business who never prices anything. I know that she sets her prices by who asks the question and I will simply not buy from here which is a shame because she has some pretty cool items usually on here table but I refuse to play that game.
Give the service and you will get the customer.