Can anyone explain the magnitude of Japanese player salaries to me?

We're all well aware there are now quite few big-name players plying their trade for Japanese teams - not just "retired" players, but more and more players in top form are cashing in for a season or two over there. So can anyone explain to me how the hell the Japanese clubs can afford to pay these allegedly astronomical salaries? Rugby is a niche sport in Japan - way behind baseball, soccer and basketball, and not even the national team attract that much attention or following. I'm aware that the Japanese clubs tend to be tied to large companies, though the nature of this relationship remains a mystery to me, and I can only suppose with most players being amateurs they pool their cash to pay one or two big-name foreigners as player/mentors, but this is just a guess. Would be interesting if anyone can explain how it works over there.

It all comes from the corporates.

Example Toyota has their own pro rugby team, and even though there may only be 6000 spectators at a match, toyota pays for it all.

These clubs must obviuosly run at huge losses

They may see it as an investment, in sporting and financial terms. If the salaries weren't so high they wouldn't attract the big names since the quality is below the top leagues. I guess the logic is that these big names will increase interest and participation and as such the league will improve, and then they will not need to pay so heavily to attact players. Japan is a huge market with a big appetite for commercial activity. A thriving and popular league could be very profitable, so the companies involved now could make a tidy profit if it takes off.

Also, I would think you may be right about putting all their eggs in on foreign player's basket. The majority of players will be amateur or on relatively low wages, so clubs will be able to afford for the vast majority of their salary budgets to be spent on overseas stars.