Well, aside from my "Come to Uruguay" pitch in the video, I think any gamer will be more satisfied spending, say, $500 to buy a ton of my products, than spending $4000+airfare to go to a hotel in rural northern england and play D&D with second-rate voice actors or pron stars who pretend to play D&D online.
The thing about dropping $500 on RPG books is the it's likely that most of the material in those books won't actually get used. Nothing against your books, Pundit, but I've bought four of your games (Forward to Adventure, Lords of Olympus, Arrows of Indra, and Lion & Dragon) and still have yet to play any of them. They look interesting, but I have hundreds of games and adventures, and most of them from any publisher get unused. I've been planning an Arrows of Indra game to run at an upcoming convention, but I haven't done it yet. Even though I'm running a D&D 5E campaign, I don't even get much use out of most D&D5E purchases. I've gotten very little out of anything except the core books.
Given this, spending more on airfare, hotel, and similar on a gaming convention or gaming event makes sense to me - because it is buying guaranteed gaming experience as opposed to something to sit on your shelf and hope to use at some point. Obviously, a $4000 price is targeting very wealthy people - but for rich people, it's buying something that can't be matched by books on a shelf. Personally, I have paid over $1000 for a number of gaming conventions I went to (factoring in airfare, food, lodging, and such). D&D in a Castle is outside my price range and I doubt I'd go even if I was super-wealthy, but I could see paying such for a different gaming experience.