The heading says it all really. An example of the stamp pictured, India SG 1525a, error of value, sold for £11,500 at Stanley Gibbons' 15 June 2011 sale in London.
The stamp is catalogued by Stanley Gibbons at a mere £1,000. A quite spectacular realisation for a modern error.
The example illustrated here was sold by Grosvenor's at auction for £2,100 in December 2009.
In examples of the 1992 India Year Pack of commemorative stamps, the lowest value of the Birds of Prey set was discovered to be a 1 r. value, instead of 2 r. as generally issued. The 1 r. value also included the species description for the 6 r. value from the same set.
It appears that it was intended that the lowest value in the set was to be 1 r., but when the inscription error was discovered after the stamps were printed, it was decided to reprint with a corrected inscription and increased value of 2 r. In the meantime, some of the 1 r. value errors had already been placed in a number of 1992 Year Packs.
By 1998, three of the errors had been discovered in Year Packs. It appears that all other 1 r. stamps were destroyed by the Indian Post Office.