From other reports, Picasso does not seem to offer discount at all.Indeed, not so many Japanese men can afford to pay that much for 120 mins of P4P.
Care to share your "secret" shops? Picasso perhaps?
It does seem the best 90.000 shop to me because i heard the girls actually use condoms. If a shop is only expensive because the majority of girls offer nama, thats probably something you want to avoid especially since nama is usually not on offer for foreigners but its still te same price.
I do think there are certainly enough Japanese guys who can pay 90.000. Yes the majority can not, like in most other places. But Tokyo is a metropolis and there are definitely high ballers here.