I don't have a lot of experience with bikes, but I used to direct import a stack of cars from Japan when I was living overseas. Side business.
The Japanese have a super tough annual inspection called a shaken which makes keeping older vehicles expensive. So stuff around 10yrs old is virtually worthless over there. 8yo Toyota Corollas with about 60,000km ( < 40,000miles ) with full electrics, aircon etc etc sell for USD80 at auction. Not a misprint, you get change from a C note. I would buy from a local agent in Nagoya ( who loaded commission ) and still only pay USD800-1000 for mint tricked up low km Honda Preludes, Mazda 323/familia turbos etc.
Cars are sent RORO ( roll on/roll off ) but bikes need to be packed in a container. ( I used to buy a few cars so occassionally would buy a Hiace van and get them to thro a dirt bike in the back - no good since US is LHD ). Bikes can be sent FCL ( full container load ) or break bulk ( sit on the wharf till space available in someone elses container ). A container generally holds about 20bikes, and should cost around USD3000 to ship to US ???
If you could get a cycle club together, you could realistically expect to pick up 20 bikes at USD3-500 each top $$, then ship the container load home.
You have to realise in Japan tens of thousands of these bikes are auctioned each week and they really are treated as junk. Can't sell them on the local market, so unless they export them they are crushed and used as landfill.