Jacko, you need to learn your way round a GAO/SAR report.
$104m PAUC you quote is the total US program cost divided by expected US orders. It's an accountants fabrication that doesn't differentiate between JSF variants and amortises US R&D across the entire US production run.
Just for fun I did the same math for UK Typhoon and got $158m. Ouch.
The US is not passing it's R&D bills onto the Brits or anyone else. Just like the EF partners don't pass on theirs. So let your eyes drift lower down the GAO page to find the expected flyaway's of the "A" at $45m and the "B" at $59m. THAT's what you need to figure the latest UK stickers. And yeah, they'll go up between now and then.
Check out this thread from one of your neighbors. Scroll down for English. Hilarious in parts.
http://www.dagbladet.no/nyheter/2006/05/01/464964.html
Don't disagree with the pig in the poke nature of the deal being offered - sign here and we'll tell you the price later. Such is life in the real world. If you don't like it, bail out of the program and come in later when the prices have been fixed. Of course that means a higher price, no UK royalties, no UK industrial benefits, no UK weapons integration and last place on the production line. And absolutely no chance of getting your sovreign thingie. Your call.