I guess the usual counterpoint is: they have to build a new track anyway (the existing one is getting saturated). Building a rail track or a maglev track costs about the same (almost all the cost is making the tunnels), and the maglev track is better, so why not go with the maglev.
It was discussed a little bit for the new high speed train line in Britain, but rejected for the reasons you state in your first paragraph. But Japan seems much less worried about reusing trains (different lines are usually operated by different companies with different rolling stock). And somehow they were able to get this project funded even though it will be many years until first service---maybe they just are more competent than the west when it comes long-term investments? :) So maybe the trade-off came out differently there...
Maybe it's a tech-fetish.
The Germans tried the same thing with Transrapid for many years (between Hamburg and Berlin), but just ended up upgrading conventional rail.
It was discussed a little bit for the new high speed train line in Britain, but rejected for the reasons you state in your first paragraph. But Japan seems much less worried about reusing trains (different lines are usually operated by different companies with different rolling stock). And somehow they were able to get this project funded even though it will be many years until first service---maybe they just are more competent than the west when it comes long-term investments? :) So maybe the trade-off came out differently there...