though, i can't say the karma required is something i agree with... either you should have more levels OR lower karma requirements (T$ maybe so too), to make it more attainable:
16th level - 3600k
17th level - 6000k
18th level - 9000k
19th level - 15,000k
20th level - 25,000k
let people have the first two with ease, then increase the curve as you go up! it feels way too consistent, and just gives me the idea of it being "another 5k achievement". The pricing doesn't seem too bad!