Actually revenue for mining PPC was at about 150% of mining BTC a couple of days ago, currently down to 75% of revenue compared to mining BTC directly. With the current crypto-currency craze you will often find a couple of days worth of demand for some weird currency in exchanges like cryptsy at a good rate. You need to calculate in fees to moving coins out of those exchanges as well though. Margins are getting slimmer lately though, too many spreadsheet warriors around ...