On Business: New vs Old Models
What he did have, though, was a shop with your more-or-less standard books and t-shirts and such. I don't know when that originally got set up, but I know it's been going for a good long while. What's more, many of his shirts speak to a broader audience than just his readers. That is, while they do reference characters and jokes from his webcomic, they still hold up as interesting/amusing on their own without the context of the webcomic. Meaning they can be appreciated by non-readers who might not care about the webcomic but like that particular illustration or joke.
Now, the first thing here is that he's diversifying his income streams. Good move, right? If you rely exclusively on one venue, it might blow up through circumstances beyond your control and then you're SOL. (Patreon might be bought out, or his t-shirt vendor might go under, or something.)
However, it seems that he's still focusing primarily on his old model: selling books and shirts and such. I get the impression his Patreon is almost an afterthought. A link thrown on the site and then mostly forgotten. If that's the case, then, great -- he's getting $800 a month for doing about nothing more than what he was already doing. Perhaps he feels he can't provide much additional value with more content specifically for patrons, so he doesn't focus on it much.
All of which is fine, but my point here is that he seems to be focusing on his old business model. Which is all well and good, but you have to make sure -- like he is -- that you're not dismissing other models simply because they're different. With as frequently as the market and the technology changes, you simply can't rely on what worked yesterday. You have to check out other options as they come out to see if they might be a good fit for you. They might not, but ignoring all of them and just keeping on as before is almost a sure-fire way to lose.