The only reason that parts for F or L cars is so expensive is because the Dealers can charge what they do, and the uneducated don't think twice about it.
I'm one of thos poor L car owners, and cannot afford to pay $ 2000 for a tune up on my Diablo. (Plugs, Plug wires, dist cap and rotor). So I do my homework, and was able to to do the same, myself for around $ 300. Most F / L car owners don't want to do that. A lot of the parts come from someone else, so it's just a matter of figuring out where they got th eparts from. For F Cars, they raidied a lot of parts bind from Fiat, while L cars robbed parts from everyone. The steering rack from Rover, Washer bottle from Nissan, brakes from BMW, ignition from Jaguar, etc. You get the picture. Ford is not much different, the lifter adjuster/followers on my Cobra R are from the Dodge Neon( SVT could not find anything in Ford inventory at the time to work for the Cobra Rs unique heads) as well as parts from the early 96-98 Cobras, Mauraders, Probe, etc.
I was glad to see the GT some to life, since now, I've got engine parts for my Cobra R (Being the little brother and the test mule to the GT500 and GT) at reasonable prices. Previous to 2005, SVT wanted $7000 per head for cylinder heads, the intake, exhaust were made of unobtainum.
The GT owner seems to be a different breed, and nowhere near as uptight as an F Car owner. Ironically, L car owners seem to be of similar mindset to the GT owners. Maybe its just me.
One day, I'll have a GT, but being in my early 40s, other things are on the radar right now.
Best Regards.