I've long conjectured that Castle and Pirates have fewer fans than the fans of those themes like to think. It's just that those fans are very rabid. So, yes, I expect this gwp to end up around $30 like most, but then slowly appreciate. But not enough (or not fast enough) to justify to buy on the secondary market.
Lego needs to bring these themes back for kids. Make sure they continue to have castle fans in 20 years. Plus, they are really fun playsets. But looking at the city theme, Lego seems to have given up on own-IP playsets.