> Do they really end up with less money if the person wouldn't purchase it otherwise?
Frankly it doesn't matter whether the person would have purchased the item or not if they couldn't make their own copy. Going down that path would outlaw all competition, or even just choosing to abstain from purchasing anything. There is nothing inherently wrong with making choices or taking actions which result in other people receiving less income than they might have in some other hypothetical scenario. What matters is that they still have all of their own property whether the copy is made or not—they are not made any worse off than they were before.
Do they really end up with less money if the person wouldn't purchase it otherwise? A realistic example I've lived, is that purchasing the software/movie or whatever copyrighted material is impossible due to its unavailability in the local market, the absence of payment methods to purchase it online and/or the heavy cost compared to the cost of living in most parts of the world.