Your mistaken, yet again. We don't do straight barter exchanges, anymore ... just in very poor places where there isn't enough cash in circulation. [See:Alberta in 1931].
When I buy a chicken at Sobey's, I'm not expecting it to be a straight barter exchange. It is not barter, nor do I expect it to be.
Cash is simply the common medium to assist in affecting a successful transaction.
I take it that you are equating barter with an opportunity to negotiate price