This seems like a bit of a strawman argument. I haven't seen anyone say that explicitly—if they have, it certainly isn't common. I have seen people say they're willing to pay for a "higher quality app," and I can see how you could interpret the implication there being that FOSS apps are shitty in comparison. For me, though, I don't interpret it the same way, and I'd assume positive intent. Some people like Sync better than the other apps and are willing to pay for it. That's it, really.