Carole...those are too cute and would make adorable price tags! As Mary said, pretty much anything can be knocked over when people are frantically reaching to grab all your adorable stuff to buy!
The first year I used those little plastic frames I had them upright and they would get knocked over too...then I switched the layout of them to make them sit the other way (with the "leg" part as a prop instead of the base....I can't explain it so well?!) and now they dont get knocked over. Plus, I can make cute signs for them and they are protected in plastic and will last thru many craft fairs until I change prices.
I have wanted to make some of those clips to sell tho....glad you reminded me of them! They are darling!
PS....LOVE the name of the biz you guys are using for the 3 of you...It's so clever!! Show us your sign you made! =)