Am a former media mergers and acquisitions banker. Here's how to think about the value of HD: Depending on growth, I'd say it's worth 10-14x the total annual profit for this year. That's a reasonable ballpark for what is effectively a subscription business.
If someone wanted to figure out how many users are in each world, we could get a reasonable estimate of revenue for HD.
For expenses, figure there is one main programer, 1-2 customer services people, and some rented hosting. My guess is that expenses are under $200k / year.