Apple can do it for $99 a year (plus thirty percent of course). Their system is by no means perfect, but there absolutely is less bullshit malware on their market vs google chrome.
This is kind of strange thought isn't it? At that rate even if people were inclined to pay its affordable to what 10% of the US or a fraction of 1% of the world.
Why would it even cost that much? You could literally use the actual chrome store for curation and make a white list of the top 100 extensions that aren't skeevy or run by skeevy people and pull in updates periodically after checking that it hadn't become obvious malware or been sold.
If you imagine that such a list would consume meager resources per person using it a million people paying 1 dollar would probably pay more than it would cost to run it. It would be easier to convince a million people to pay a dollar than it would be to convince anyone to pay a thousand per year for chrome extensions while they are using computers and OS which cost them less combined.