Filing fees, while costing money, are nowhere near the same cost as the hourly pay for most attorneys. I'd expect that even if the case continued for years, the expenses could never go above a few thousand a year. (which would still be quite a lot for expenses)
As far as drawing a lawsuit into eternity, that isn't possible. (eventually the justice presiding will catch on/snap). However, it is standard to play games to delay the court appearances to later times, and file many additional documents in the interim that need responses. As reading and responding to every filing costs time and money, it isn't very difficult to force attorney fees into the 50k-100k range (In high profile cases like this one, I'd expect much, much more). In most cases, people can't handle an expense like a lawyer for more than a very short term (even less than the 2 years you quoted), and the lawyer either stops getting paid regularly and pushes for settlement, or the client gets tired of paying, and drops the case. If you want a citation, go buy an account on loislaw and look for any suits that were dropped after extensive litigation, yet without resolution. Usually attorney fees were the cause (although it isn't officially stated, since it was just dropped).