The great forgers of the past - Fournier, Sperati and many more whose names are less familiar - took their work seriously. They were very knowledgeable, they had remarkable craft skills, and they invested heavily in the reference material and equipment necessary for their work. They approached their business as a life-time commitment. They could claim a place on the Roll of Distinguished Philatelists.
Nowadays, forgers are looking for a fast buck (preferably a hundred bucks) on ebay.
First of all, look at this 1920 document from Erivan: