I've seen some of their prices on the website and also heard second-hand from colleagues and friends. Imo, and I could be wrong on this, the only way their business model would work is if they bartered miles like buying them in bulk from other customers for under a cent... or scammed/stole it, cause (a) some of those J fares are too cheap to not be through mile redemptions, and (b) even purchasing those miles directly from the airline at the best possible offer still returns a net loss. Too shady and against T&Cs of every FF program.