The old nodes are cheap because the investment has been fully paid off. There are only running costs and maintenance remaining. However, expanding productions of older nodes will be more expensive, especially if the equipment is not available in bulk anymore. Probably not as expensive as a new node though.
Right. pre EUV, the only reason older nodes were cheap is because you didn't have to build a new fab. Now though, EUV machines are expensive enough that it looks likely that the pre-EUV nodes may remain cheaper pretty much indefinitely. 22/14nm is pretty power efficient, a lot simpler to make.
