I agree that bargaining is inefficient for small transactions but it is the basis of business, everywhere in the world, regardless of whether or not there are price tags.
Ah yes, but that's thanks to the absence of information. And technology (internet especially) are filling in the missing info, and putting the middle men, a.k.a those who bargain, out of business.
The railroads did exactly the same thing with other middle men. In general, that is how markets become more efficient, by putting hagglers out of business.
