It's not hard to fathom -- but that's not the issue. The dev decided to make an ad-supported app in an ocean of free, no-ad apps. In the views of some folks, the ads and the cost to remove them are too much. Some say it's worth it; some say it isn't. That's the beauty of free choice.

The dev could have opted to take donations if they wanted to try to recoup development costs. Frankly, they could have read the room and noted that there's a limited market. Given that there are numerous other options available (many of which are free and open source by choice), it's a hard sell to say one dev should independently be paid simply because they chose to be regardless of the market condition. This isn't a moral or ethical issue -- it's someone arbitrarily throwing a number out for payment for an app that runs on a free and open source platform.

The Sync dev is one guy who has bills to pay, he always interacts and listens to feedback and is constantly updating the app.

This describes the situation with most of the other devs working on the alternative apps. They've been extremely quick with fixes and improvements. Again, no ads in those. Sync is not the standout you seem to think it is.

Why is it so hard to fathom that some people deserve to be paid for their hard work?

If anyone should be paying for anything on Lemmy, it's for the hosting of Lemmy itself. Sync can't load anything but its ads without that. I certainly hope people follow this logic when asked to pay for their bandwidth, which is the only place it seems to actually apply.

But hey, to each their own -- if people want to pay $20 to cut the ads on one specific app, they should absolutely do that. Don't frame it as anything other than that though; it's simply disingenuous.