Gold, 60,000 miles
Sorry, but flying less than this doesn't make you "elite". The current Silver and Gold categories are like winning Miss Congeniality. We applaud your efforts, now get the hell off the stage. These are like B and B+ students. Great job, but no Dean's List for you.
Flying one round trip per year to HKG on an unrestricted ticket doesn't make you elite.
Why 60 and not 50 as an "achievement"? I'd argue that a one-time unrestricted fare to HKG is more valuable to the company than 6 $300 transcon rt'd to get silver. ITs not like silver is worth that much.
Remember the program is a lot more about psychology than actual benefits. They want the next incremental level to be close enough to motivate people to fly. Tons of people are willing to do a run just to get silver. That's lots of revenue left on the table at little expense. They don't give silvers anything more than GM's with a credit card except the 25% bonus, and day-of-departure E+ (and the very occasional upgrade after everyone else got theirs) which doesn't amount to much at that level of flying.