In my opinion/experiences, driving my NSX has cost as much as driving an accord, maintenance wise. Sure the engine parts and other drivetrain parts are more expensive, but this is a Honda. That stuff doesn't break.
Sounds like your uncle needs to stop going to the dealership for oil changes ;-)
Porsche dealerships use Mobil1 Synthetic, which is one of the pricier brands. I've heard the OEM filters are also quite expensive. Still.. $300? I thought the $65 change I've been charged by an Acura store was ludicrious.
Typical price for an NSX oil change is $20-30 with conventional oil, $40-60 with synthetic oil.
If you take it some place (like your dealer) where they don't stock synthetic in the recommended 10W30, they might let you bring your own oil and change it for you.
Also, the oil change takes 5.2 quarts. Most places will let you take the extra 0.8 quart with you to use for next time (but many places will just forget to give it to you if you don't ask about it). Bring a gallon ziplock plastic bag with you to put the oil container in, as it may be greasy.
The NSX is one of the easiest oil changes that I've done. It takes very little time and I actually enjoy it. You can even get the little windshield reminder things at O'Reilly's for free. I'm more comfortable doing it myself than worrying if the dealership replaced the crush washer, torc'ed the filter, oil plug correctly, put enough or too much oil in, etc....
I paid about $250-$270 for oil change for my Porsche 996. It holds about 8qrt of oil. The Mobile 1 the dealer uses is more particular to Porsche, but should be about the same price as other weight mobile 1s. The labor is not that hard like on the aircooled Porsches, so I guess I'm just paying for the name. I have since then stop going to dealer for small services. 97+ NSX is definitely going to cost less to service.
During my "January Thaw" drive yesterday, I stopped at a gas station and a gentleman pumping gas next to me came over and told me he had an NSX once, how he loved that car. He turned it in and ended up getting a Porsche 911 and told me how much he regretted that decision, citing maintenence costs as one of many reasons. He winked at me and said " man, do I miss that NSX".....