I read one place that it is 25 shots for 50 cents, but I don't know how old that info is - here is some interesting trivia about it also!
Mosey on up to the Frontierland Shootin' Arcade and pickup a genuine refitted .54 Caliber Hawkins buffalo rifle. Put in a couple of quarters and take aim at tin cans, gravestones, tree stumps (try and hit the possum that peeks out every so often), and other animated targets. Boot Hill is themed with 97 different targets to shoot at, and the landscape includes a bank, jail, hotel and cemetery. When you hit one of the targets, many of which are moving, they make noise, move and provide a few other surprises.
The Frontierland Shootin' Arcade is set in Boot Hill, in the year 1850. This is one of only two attractions that require an additional fee (the other one is the Penny Arcade on Main Street, USA)
When the arcade first opened, real lead pellets were fired from the rifles at the targets. Other than the obvious safety concerns, the rifles soon had to be refitted to no longer shoot these projectiles. The real reason they were modified was paint. Paint? Yup... because the pellets chipped the paint off the props in the attraction, it was necessary for Disney maintenance personnel to repaint the attraction every night. Over the course of a year, it amounted to over 2000 gallons of paint!