They are crafted. First ones were sold for about 3k peds. Today you can get for 250 peds or even les in auction or private shops. Crafters don't craft them as they are hard to sell. Also expensive to use on lover level trees and wood and residue hard to sell because housing and fruit farming is kind of abandoned project by MA.. You get little more skills with ph 3 but pay more its decay repair too. For only skilling is better to remain on TT tool and lvl 1 trees. But if you are silly skiller then ph 4 is your tool, crafted and limited, you get a lot more mats but it have mad decay too. Btw check auctions on all planets periodically and it will eventually pop up.
but do you get more wood with the ph 3 than ph 1? or a different type of wood? also should use ph 1 for level 1 and the ph 3 for level 2 to 3?
I know it sucks to advice people to read into things...it really suck...its beyond polite... But why dont you read into things 1st ? ;D Parts of the community built the entropiawiki : http://www.entropiawiki.com/Search.aspx?searchtext=Terratech&type=search More decay, more wood.
You cannot find level 3 trees with the tt ones. So there is a use if you want to make your own planks to build your snug. Level 3 trees used to have some markup.