Underground Comix are known for using different prices, covers (art or color variations) and/or interior content to distinguish between printings.
All printing say which printing in the indicia information.
1st print July 1972 and 2nd print March 1973 have 0.50 USD cover price.
3rd print October 1974 and 4th print October 1975 have 0.75 USD cover price.
5th print July 1977 and 6th print August 1978 have 1.00 USD cover price.