MSOCS,
The cost is, alas, high in almost ALL early aircraft development stages but, for F-35, they are already tapering towards the approx. $80-90M per aircraft (F-35A) forecast for Full Rate Production from 2019+. Sustainment costs are key though.
Do you really believe $80-90M by 2019? What you are currently seeing from the JPO is creative accounting at work to say what a good job they have done in ratcheting the cost down. Don't look at what they advertise, look at what they are asking for in funding from Congress and the number of aircraft it covers. It isn't $80-90M per aircraft, think higher prices... And as time goes on, the goal number will drift upward, not downward, no one will remember.
As I said before, hope the UK has pre-paid for theirs in prior year Pounds while identifying every aspect that is to work properly upon purchase (warrantees are important these days). Maintenance costs remain a huge unknown, but I can tell you a Mercedes Benz (F-35s) costs far more to maintain than a Honda Civic (F-16s) based on personal experience. A lot of the difference has to do with the electronics, sensors, etc.