This is the magic of miles in some cases.

For instance, you can travel in the USA IAD-SFO for as little as, say, $350 or $450 on UA. But an unrestricted Y ticket can cost $2200 or so.

Yet you can pay the equivalent of $400 or $500 in the form of 25,000 miles, and get the equivalent of a Y ticket. There are some restrictions for the "saver award", but essentially you can travel on a moment's notice and not have to stay over a Saturday night and change your dates.

Int'l business class upgrades illustrate it too. A C ticket can cost $5000 or so trans atlantic, or you can pay the equivalent of far less in the form of miles for an upgrade.

In some cases miles are worth a lot of cash.