Miles versus Cash

Just been on with FC re booking an additional family member on Y flights we booked using miles and discovered that the cash ticket (which earns miles) costs $25 more than the taxes and fees for using 20K miles. When I enquired about why on earth anyone would book Y miles tickets if the cost was nearly the same, I was told that VS 'absorb' the fees for cash tix. When. wondered why BE a FC member (I have been one since the first flights out of BOS over 20 years ago) agent gave me customer service e-mail--which I will use.
I have had a look at booking PE using miles as one ways-- am I right in thinking the fees are considerably lower than RT?
I have had a look at booking PE using miles as one ways-- am I right in thinking the fees are considerably lower than RT?