How much was a shot of whiskey in the Old West?

I'm curious to know, how much did a shot of whiskey typically cost in the Old West? Was the price standardized across saloons, or did it vary depending on location, time period, and the quality of the whiskey? Did the price fluctuate with the availability of the commodity, or were there other factors at play? I'm fascinated by the economics of the Old West, and I'd love to gain a deeper understanding of the cost of a staple like whiskey during that time.