why nmc is going down like this!? 0.236 $!!!
Between around beginning of 2015 and mid 2016, F2pool had a majority of Namecoin hashpower. A few months ago several other mining pools started merged-mining NMCs, too. Therefore F2pool's hashrate share went down way below 51% (currently 35 %) which is good news for decentralization. The bad news is that one or two of the new mining pools (HaoBTC and possibly ViaBTC) don't pay out the NMCs to the miners but most likely dump all the mining returns at the exchanges (btc-e, poloniex).
Too much supply while too little demand = lower price. Setting up a named ZeroNet
page, for example, costs you far less than 1 NMC including update fees for quite a while.