The Yokohama Bay Stars will be meeting with officials from Yokohama Stadium some time this month in order to work out their next contract extension (their last deal was a 10-year deal that ended at the end of the 2010 season). Yokohama Stadium president, Hiroshi Tsuruoka (鶴岡博), told reporters that negotiations weren't all or nothing and that they'd be willing to talk issues out even after they sign a deal.
The Bay Stars have mentioned their contract with Yokohama Stadium as being part of the reason why they're continually in the red. In addition to the 800M yen rental fee, Yokohama Stadium also gets 25% of all ticket sales and revenue made from advertisements placed inside the stadium.
It should be noted that stadium officials decided to install new turf at Yokohama Stadium this winter (construction should be finished by the end of February) at a cost of about 350M yen and will probably mention that during their contract talks with the Bay Stars.