Aside from places where you buy and sell domain names, there are some companies around that support the business of domain flipping. GoDaddy is one of the bigger names out there that does. There, you can not only trade domain names but also park those you’ve bought. The buying, parking and selling is relatively painless and all you must give up is a small percentage of your selling price.
Justifiably, any attribute or factor that is known to be influencing prices, is doing so as it leads to demand. On how easy basis of such factor demand is raised and thus the price. Hence, these domains of media like segments as you say like http://www.hindi.media gain worth from the same factors that lead to demand. When price is enhanced or goes premium, the domains are thus known as premium domains.
The domain name industry is quite similar to the real estate industry in a lot of aspects. There are end users, brokers, consultants and domain flippers or “domainers”. Domain flipping works similarly to buying a house, renovating it (or even sometimes just sitting on it) and then selling it again at a higher price point. The gist of it is: you’re purchasing a domain name and betting it’s worth (or will be worth) more than you paid for it. If you’re right, you get a nice paycheck and move on. Those who make a living out of this just rinse, repeat, and scale.