Since nearly all US-based airlines set 25,000 flown miles as the threshold for elite status.
That is the case with CO - where one year I got my husband CO silver elite status. And I now remember how I did it. We flew to Japan. Got one free BF ticket - one paid (only cost about $2.5k - a relative bargain IMO). With the mileage - and the mileage bonus for BF - we only needed a few more miles to get to that magic 25k. So I booked the cheapest east/west coast ticket possible at the time - which happened to be Jacksonville to San Jose California. The tickets were about $200 each. Extra bonus - relatively inexpensive Four Season in Palo Alto having a buy 2 nights - get 1 free offer. Extra extra bonus - it was a nice trip to a part of California we had never seen before.
Only problem is silver elite never did much for us. Got one upgrade on one segment of a domestic flight. And this was 5 years ago.
Today - an important perk - at least on a relatively inexpensive short haul flight - is not having to pay for checked baggage. Way I look at it - annual fee for most airline credit cards about equals the fees for 2 checked bags on 1 round trip for 2 people. Sound about right? Does lowest elite status get you free checked bags on most airlines? Robyn