In general, long (both regional and national) distance and international calls become MUCH cheaper. Pre-1984, we used to worry about how much a call to a relative in another state would cost and we'd keep the call as short as possible. International calls would cost a goodly portion of the national debt.
However, a POTS line for local (or incoming) calls only has become more expensive; it's now $20 or so instead of $6 (and that's assuming that you have long distance disabled or you have to pay an additional set of fees for the long distance privilege).
Fortunately, the advent of DSL, cable modems, etc. have eliminated the need for modem lines. I once had four POTS lines (voice + three data); now I have just one.
I understand why many of the kids choose not to have POTS service at all. The argument about POTS being more reliable than cellular/VOIP doesn't hold in my neighborhood; POTS *always* goes down during a power outage (an event that happens several times a year).
-- Mark --