I haven't priced an RTW with all airlines, but my experience suggests that JL may be cheaper than AA, BA, or QR. A couple of times when I used an AA SWU to upgrade an AA segment on a JL-issued RTW, AA threw conniptions, saying JL hadn't charged all the carrier overcharges and AA couldn't reissue without collecting them, but I was eventually able to get them to do a straight reissue.

JL is more cumbersome to deal with for an RTW than AA, for sure. With AA, you call, wait, and get an RTW-experienced agent. With JL, if you call the U.S. number exactly when they open at 5am Pacific, you usually have no or a short wait, but it's luck of the draw if you get a Los Angeles or overseas agent. The L.A. agents all seem capable and experienced with RTWs, while an overseas agent will first try to help, then put you on hold to "consult the relevant department," then transfer you. If lucky, they transfer you to L.A. or an agent in Japan who knows RTWs. If unlucky, it's one more transfer. A transfer typically involves a lengthly hold (I call when I have other stuff to do while the call is on speaker). If you don't call the U.S. number the instant they open, there is usually a lengthly wait. You can also call Japan, but they often bring a translator on the line.

That said, I have purchased several RTWs over the past few years with JL, typically AONE5 or DONE5, with open-dated segments, and have made changes multiple times. It just isn't as easy as with AA.