[Answer]

There was this topic: https://bitcointalk.org/index.php?topic=17456.msg223734;topicseen#msg223734 but it died without providing full answer.

To recap:
- How much does it cost to register a .bit domain?
Answer: cost is variable and can be calculated here: http://dot-bit.org/tools/domainCost.php
- What is the upkeep on a .bit domain?
Answer: upkeep is variable, see above.
- Can the price vary? If so, how much?
Answer?: yes, it can but depending on what?
- Can I trade USD -> NMC, or do i have to do USD -> BTC -> NMC?
Answer: currently USD -> BTC -> NMC

My question:
1. Is it possible to register a .bit domain for more than 12000 blocks and not have to update the domain for the next 100 years?
2. Why does name_firstupdate lose coins and is it necessary for proper Namecoin functioning?

Key question:
What problem does Namecoin solve really?