I saw that movie once some years ago, but don't remember that scene. But if somebody complains about a $5 milkshake, it could be just a way of complaining about high inflation, especially if they can remember when they were a kid and a milkshake cost 79 cents

It's pretty much what I'd expect to pay for a drink

A milkshake isn't a drink. It's a milkshake. It's like complaining about a $5 ice cream cone and then someone else says Well, that's what you would expect to pay for a dessert. There exist places that charge $10, $20, and on up into the stratosphere for a hamburger-- but that doesn't make it a reasonable price.

Not terribly expensive, but not cheap either.

The milkshake in the movie was not your everyday milkshake, it did contain an extra alcoholic beverage ingredient - Vincent's favorite. But he felt it was overpriced.

$5 for a milkshake in the early 90's would have been more expensive than normal. Especially in America where dairy products are subsidized and cheaper than other first world nations.

As Rugles says, it was expensive for that time.

Depends on if they use soft serve or high butterfat ice cream.

Food (and drink) have been relatively affordable in the USA for several (as in two) hundred years. There have always been high=priced presentations from time to time, but only for the elite with bucks to burn. Average Joe (and crook) stretched their dollars so, yes, it was expensive. But more importantly this self-referencing film is about PULP FICTION as portrayed in Pulp Magazines from 1910-1948... thus all the gags are based on that time frame, when a coke was a nickle, coffee was a nickle and refills were free, and a 9 ounce roast beef sandwich between a quarter loaf of bread with mustard and au jus with two dill (whole) pickles for a quarter (25 cents). So yeah, a five dollar milkshake was WAY out of line!

(Tarantino had no clue, but knew a good line when he saw it, milked and shook -- pun intended -- a literary era.)