The question arguably has little to do with managing a site, or in this case assets related to one. While there are plenty of questions accepted regarding finding where to register a particular odd TLD and so on, those are actual practical matters directly related to running a site. This particular question is really just economics.
[Because there's so much domain talk otherwise, I do agree John might've provided some context in this case, which may even have been something entirely other than what I said above.]
A seller can set their product at whatever price buyers will tolerate. .tv domains were launched at a relatively high price because the TLD controller figured TV show producers would pay a premium for eg. americanidol.tv (I've seen little evidence that plan worked out.) In contrast, most registrars seem to offer .biz at low prices because nobody ever really took that TLD seriously and it seems overrun with spam sites in my experience.
There are a few other instances like .tv where someone can point to specific reasoning for a given TLD's pricing, but ultimately there's no real answer to the question other than "That's what [whoever] decided the price would be."
