It's the same with music piracy. Sure, one might buy 1 CD. Even 10 CDs. But very few people would buy those 20GB+ of worth of music they hoard on their harddrives. It's something they take for free but would never pay for.
The difference with music is that you can make a partial purchase because the product is sliced into small enough pieces. I may have the whole discography of a band spanning decades, but I only buy one or two of their albums. At least they still get some money that way, so maybe they don't have to feel the same frustration that you do.
In that sense piracy enables some sort of involuntary "set your own price" scheme. But that only works if the product can be sliced down into small enough units enabling the consumers to set their own price.
For software this is more difficult, but not impossible. For example adobe products or microsoft office get pirated in private environments but paid for in commercial settings. The private copies serve to entrench the product in the market, even if they don't generate a direct profit by themselves. So even there is a difference between what people are willing to pay and the retail price of the products.