Zaishen Title - double faction?

Hi
is there any "event" that multiple the zaishen points for each key? (from 5 to 10?)
because i heard when people said that they need 1 mil for z-keys and someone told them to wait for double faction and it will cost them only 500k

The isn't an event that will double the amount your z-keys give the title. The double faction they are talking about would be any pvp weekend event. During these, all the faction you gain, say from a kill, is doubled

Creating a bigger influx of Zkeys, though they won't be any cheaper than 4k.

The price never goes below 4k, like Arduin said.
They are normally between 4.5 and 4.7k each. On double faction weekend, people are can aquire them twice as fast as in the time it takes to normally get 5k faction for 1 key, they are getting 10k faction.
This however, won't make the price go down. People will still weasel every penny they can out of you. The lowest I've seen them on a double faction weekend was 3.9k each