As a buyer, and reading through this thread, a visible price on the card isn't a one-size-fits-all answer to me. If it's something rare (to me), or a priority card, I'll ask if no sticker. If it's a relatively commonly findable card with no sticker, I might ask on a specific card, and based on that answer I might ask on others, or not. Or I might just walk on by. For the National, it would also greatly depend on whether it's Wednesday or Saturday.
Regarding the "I'm just looking" type of question. When asked what am I looking for, I frequently respond by saying that I couldn't really say because a lot of times I end up buying things I'm
not looking for. And it would be the truth.