São Tomé and Príncipe honored Mahatma Gandhi by issuing stamp of him along with India's Flag in a souvenir sheet with other great world leaders such as Washington, Lenin etc. in 1980 to celebrate 5th Anniversary of their Independence from Portugal.
This stamp was sold recently for $1.81 in auction as well as Fixed price. I think it's a correct value of stamp.
This stamp itself has another Gandhi (Gandhiji) Stamp of 25 paisa from India which is very commonly used and most recognized Gandhi stamp in India. This stamp is first Mahatma Gandhi Stamp from São Tomé and Príncipe but recently they are frequently issuing Gandhi stamps to make money which itself degrade value of their stamps so please know what are you buying.
Generally small countries will contract their stamp out in order to get free printed stamps for their use and contracter makes money by selling this stamps to us.!!! Check following links to see who is contracting for Sao Tome.
(My Son's blog http://usapostman.blogspot.com)