The Simple Answer is YES!!
So many items to sell you don't have time to shout prices off the top of your head!
I did an experiment years ago when I put out a bin of stuffed animals with a "MAKE AN OFFER SIGN". Many people picked up the toys but were too shy, or did NOT want to face CONFRONTATION over haggling over a price. Needless to say, I did do not sell alot of the stuffed animals that year. The next garage sale I priced the stuffed toys and sold out! Buyers want to know UP FRONT what they will pay for things. This is one of the BEST tips I have.
Garage Sale Groove!!