The most recent data I've seen on this is Trish Loughran's The Republic in Print: Print Culture in the Age of U. S. Nation Building, 1770-1870. She puts the ceiling at 75,000, but details an argument for it being a much lower number than that. The limitations of print runs limited the absolute number of copies while the geographic restrictions (16 of the 25 printings were in Philadelphia) made wide diffusion difficult. Paine, of course, is famous for outrageously over-stating how many copies were in circulation and some of those numbers, unfortunately, were pasted into textbooks.