Instead of watching ebay for the book RAILROADS OF THE BLACK HILLS go and look at one of the websites serving used book dealers. Two of these are abebooks.com and bibliofind.com. Some dealers are on both services.
I did a quick search by title and at abebooks it produced 45 copies and it looks like about the same number at bibliofind. The prices range from about $15 to over $100. Most are between $20 and $30.
Good hunting.
Brian Norden