at times, some people are too rich and desparate and allow you to get some good money for lvl12 elites (the useful classes of course: rep, eng, ftr).
highest i've sold was around 8 mil. but usually its lower (still planty for you to buy any regualr battleship). i've seen ppl go over 10mil. but you'll have to be very patient for those
of course, it depends on the market too. ex. sudden high demand for italian sailors when they first came out.