If today's tomatoes aren't looking so great, why should I pay the price charged for perfect tomatoes? If I'm willing to put up with some defect in a car/shirt/refrigerator for a lower price, I believe I'm competent to make the contract.

Sure. In the fixed price world, we do that with multiple stores with, say, outlet malls and TJ Maxx mostly selling the seconds. Although I've certainly bought marked down refrigerators which had dents and so forth. But, yes, there's an efficiency in those cases to being able to negotiate the price.

In the business to business world we call it negotiating, and it goes on all the time.

True. But that's a transaction between highly specialized people who have a much more keen understanding of the values than a foreign tourist.

Another prespective is offered by Wal-Mart which haggles/negotiates with its suppliers but not with its customers.

Rather than have someone tell me what something is worth--take it or leave it--I'd much rather be able to argue from the the point of what it's worth to me. Sometimes I end up 'overpaying', i.e., paying more than the item's cost + reasonable profit. Sometimes I don't. I guess that's inefficient to some extent. But I feel I come out on top far more often than otherwise.

If today's tomatoes aren't looking so great, why should I pay the price charged for perfect tomatoes? If I'm willing to put up with some defect in a car/shirt/refrigerator for a lower price, I believe I'm competent to make the contract.

Now, I don't want to have to haggle over every damn thing; fixed prices do have their place. But I certainly do enjoy the give-and-take, particularly when I know that both I and the seller think we struck a good deal...