I think you are confusing the "B" story stuff with the serious stuff. There is no reason why garlic, coffee, etc couldn't be as readily available for the crew as, well, oranges. I was in the Navy for 26 years, and we never ran short of coffee even on Gonzo Station in the Indian Ocean (a hell of a lot further from anywhere than B5 was). Dairy products were a problem (and eggs, which cannot be frozen), as were fresh fruits and vegetables, but coffee, never.
The idea that space travel is incredibly expensive doesn't really hold up very well, either. I mean, if they could have an Elvis convention on board, it cannot be all THAT expensive.

Can you imagine an Elvis convention being held in the 1990s in a place only accessable by Concorde?
I think you just have to accept some of the "B" story stuff with a grain of salt, and recognize that not EVERYTHING is well-thought-out.
But I think that, so long as we are rationalizing this, Joe D has it right, with a further twist of my own: the problem wasn't getting the stuff from Earth to B5, it was paying people to track this specialized stuff down on earth and getting it to the spaceport.