The piracy argument is different to stealing because of the simple fact that there is an infinite supply of digital goods. If I steal a laptop, there is a real cost to the supplier, because they have 1 less laptop to sell. If I pirate a piece of software, they only lose out if I would have bought the software had piracy not been an option. "lost sales" are hard to quantify.
Disclaimer: I don't pirate, and I sure as hell don't steal.
There is a virtually (that bandwidth and storage aren't infinite) infinite supply of any digital good.
If nobody pays but everything else keeps costing money, there won't be any new digital goods. So you can't say there's an infinite supply of digital goods.
Disclaimer: I don't pirate, and I sure as hell don't steal.