Here are a few charts like the ones I use to regularly post. Anyone can make these by downloading (cut/paste) their own sales from the store report and loading it into a spreadsheet program.
I go one further step and to do some projections. These obviously change, but it is interesting that a year ago when I had sold about 3500 cards to date, I forecast I would hit 10K cards sold by Feb 2011 and it still indicates that. This also helps one predict future income.
No one can yet live on GCU sales today, I believe, but one day this could be in the cards, so to speak.
I am far from a "Top performer," but the message is that in time all the effort will be rewarded, perhaps.