International collaboration helps JSF's credibility, but the STOVL version is the most expensive, yet will be built in the smallest numbers.
USMC requires 600, the RAF/RN 150-160, Italy, (assuming JSF will be for the carrier wing only), probably 30-40.
Another problem is that USMC has the most urgent requirement, so the most difficult phase, the testing of STOVL version, cannot slip too much.
Possibly USMC might then be forced to take some CTOL/CV versions as an interim buy, thus undermining the STOVL version.
The RN could then be forced into the CV version, so a decision on the JSF's future is needed soon so RN knows what type of carrier the CVF will be. The UK taking the CV version will put pressure on the RAF to take the CTOL JSF as a Tornado IDS replacement, which would not meet the probable requirements.
This would damage European industry as it would blow away a follow-on to Eurofighter. As the only likely major European military aircraft programme post Eurofighter would be the Tornado replacement for UK/Germany/Italy, and possibly also France's Mirage 2000D/H fleet.
It's good to be on JSF, but it is no subsitute for a European fighter design and build capability.