My calculations are with the assumption that you will sell every single card you get.
And this is absurd. It is more likely that you will keep most of the cards for your collection and sell only the copies above 6.
So this brutal exaggeration of my "card per day" should nullify the effects of new cards appearing.
If I used my "eye of economist", I would say it would be 3-4 cards per day. No calculations to back it up but who says economists need those
Edit: Eye fails.
More than 4 is closer to reality.