The value is highly subjective, it depends on how you value and spend the miles.

Some people who fly a lot do not want to spend their AP miles on more travel, they may spend on toasters and TVs. Others will use the AP miles to book a Star Alliance long haul holiday in Business or First Class, or some may use them for short haul flights.

Only you can determine what is a valid estimate to you.

FWIW, I use mine for long haul (NA to NZ and back) trips as well as short haul for friends and family. My short haul destination or departure point is very expensive in actual $$ terms, so 15,000 miles becomes good value.