I doubt the WTBS has a huge amount of available cash. If they are smart everything beyond immediate need is invested in something. Using a bond company doesn't require a huge amount of cash, so they don't have to sell their investments to have it sit in the court's account doing nothing.
Back when I was in (OK I'm dating myself here) when the Watchtower and Awake sold for .25 each they moved about 10-12 million copies of each issue. They didn't care if they were placed or not because they got the money from the publishers when we picked up our magazines. Thats two to three million dollars four times a month. That's a cash cow no matter what business you're in. Since they went to the donation arrangement I imagine they've been more strapped for available cash.
Absent financial transparency there is no way to judge their financial status. They're showing signs of financial strain. Going to a pledge contribution might help make up for the loss of revenue from the publishing arm.