Probably most pirates would never buy as many games as the ones they pirate, and many of them start pirating less and buying more if their income grows or if their personal income simply start existing if they were young pirates not working yet.
I used to both buy and pirate games many years ago, but the last time I pirated a game it was just because it wasn't on sale anymore, as soon as I found a regular bargain edition copy I bought it, it was Planescape:Torment and it fully deserved my money.