Namecoin used to be a much smaller niche than Bitcoin, the prices of Namecoin is extremely low compared to that of Bitcoin. One Namecoin is only about 0.006 Bitcoin and the difficulty to mine the Namecoin is tremendous due to the new merged mining. The difficulty of mining Namecoin at this moment is 639,363 as compared to Bitcoin 1,577,913 and it is just worth 0.06 of Bitcoin. It is more cost effective to buy Namecoin from the market if you need it for the Dot Bit registrations and functions. Reason being merged mining allow Bitcoin and Namecoin and other coins to be mined together hence increasing the hashes and the difficulties and driving down the prices of the other coins tremendously till they are nearly worthless.