Besides the F35 being as agreed expensive, as the IOC is so delayed, nations who bought into the cheap to purchase and cheap to operate 5th generation fighter / attack plane, are having to fund the continuing high costs of their long in the tooth 4th generation fleets.
A combination of the above and the recent financial uncertainty of most of the world would suggest that the resources are not necessarily there to purchase the planned number of planes. Or am I missing the plot?