The point about how much they cost could always be viewed as 'is it worth it?'
For the F-35's capabilities, is the expense worth it compared to a legacy jet? This depends on what the politicians/strategists etc envisage your country's military doing, and against whom, in a certain timeframe.
Then the next question is, for the Nation, is it worth the national expenditure? For the UK, with it's industrial share of building all the future F-35s, the answer is probably yes as the income and jobs generated covers the cost of the aircraft (according to some figures). This would not happen if we had bought off-the-shelf F-18s, Rafales etc but would have had a bearing on marinised Typhoon or Sea Gripen to a greater or lesser extent.
For the partner nations such as Australia and Canada there is some maths to do to figure out the overall cost to the economy of being in or out. The UK paid a lot of money upfront to be the only other Tier 1 partner but got a lot back for that National investment.
The squabbling about the actual unit cost is pointless. Early jets will be expensive, later jets less so. I am sure that long after the F-35 is combat proven the arguments will rage on about is it actualy worth all the money spent. For instance, was Typhoon worth all the time and money spent on it for the capability it delivered during the Libya ops, versus buying Rafale? It depends very much who you talk to, but what it has done is provide a lot of jobs in the UK that will continue as foreign sales are pushed.
There is a much bigger picture out there than just "$xxxM only buys you 1 jet" tabloid headline figures.
