The question is buying expensive vs buying inexpensive, which is simple supply/demand economics. I'd go even further, and suggest that the "loss" is fictitious. It is really an overestimate of the sales on the proprietary software vendor's part.
I'd go even further than that, and suggest that open source doesn't necessarily take away from software vendors, but allows more users access to software that they normally wouldn't pay for.
When I see software labeled 'Free Trial' next to one labeled 'Free', I almost always go with the latter. But then again maybe I'm just cheap.